Cars should be taxed at £800 per year - to understand why you'll need to read below.
They don't want to because the UK makes the experience stressful.
I'll give an example of how a train journey should happen, get on the Elizabeth Line, go to Paddington, change to an express (sit down doors close), get off at Reading walk over to platform 2 get in a train to Basingstoke wait 5 minutes for the train to go, get off at Basingstoke and change platforms then wait 3 minutes for the next train to arrive and be ready to leave.
However that was just shear dumb luck at Reading and Basingstoke, rather than having trains running at least every 20 minutes to ensure that was the norm (even every 30 minutes would be a significant step up for a lot of the network). If you have hourly services (which a lot of the network has) if a connection is missed that slows you down a LOT, if you've got more than one such connection you're not going to risk it.
Arguably the extra cost of running an extra service (where the line could allow it) so local lines were less likely to be so poorly connected (given the significant cost of maintaining a lightly used section of line) would be fairly limited compared to the overall cost of that line. Whilst it would ultimately probably increase the overall cost of the rail network, it could actually aid with local traffic congestion as going by rail becomes significantly more viable.
Not related to rail, but public transport, locally one of the next villagers over is about 3 miles away and the walking route is unsafe (as a road designer I know it is, if I tried designing a road with poor visibility at crossing, crossing which are the queuing side of a stop line, open drainage features across a footpath and paths which don't follow desire lines I'd get told to try again in no uncertain terms) so should be an ideal route to use the bus.
However, the bus stop is about a 15 minute walk from my house, the bus is hourly (so I really can't miss it, as I was wishing to use it for getting to/from work) and the times were bad for when I wished to use it (either arrive late or nearly an hour early or leave work early or fairly late), as such I cycled.
The reason being I could cycle in 20-25 minutes (including the time to get my bike out and secure it at work), which was about the time I'd need to leave home before the scheduled departure of the bus to ensure I didn't miss it. With the added bonus of being able to make that trip at any time I liked (and being a lot cheaper, even accounting for new lights, power for my lights, better waterproofs, and any other factor you could think of - maybe even a new bike after 3 years).
If the route has been every 30 minutes I may well have opted for the bus. That now frequent bus may not cover it's costs, but it's likely to remove more cars (and therefore reduce delays) than the impact it has by running.
There's a major junction which is near capacity (at peak times there can be noticeable delays), a more frequent bus isn't going to stop that from happening (as there's significant numbers of longer distance travellers) however it could mean that the delays are less of an issue
To the extent that it could mean that the very costly upgrades which would be needed to improve capacity wouldn't need to happen for a long time (if at all).
Yes the bus isn't going to replace all the traffic, but that's not what we need it to do, just be better so 20 fewer cars run through the junction (which is the equivalent of adding an extra second of time every 90 seconds in terms of junction capacity) in the peaks.
Whilst 91 seconds Vs 90 seconds doesn't sound a lot, most green lights at a signal junction are between 7 seconds and 35 seconds (or enough time for 3 to 15 cars to get through) and the next green light is 60 to 90 seconds since the start of the previous green light.
Therefore, for most people (on the arm the bus benefits) that's one less green light they have to wait for before they can get through in the peak hours. That's one minute saved.
Repeat that across 5 junctions (where you have to wait for more than one change of lights to get through) and your journey to and from work is about 25 to 30 hours less each year (assuming a 5 day working week and not being at work 31 days a year, however allowing for the fact that school holidays you get that benefit, if not more, already). That's not even allowing for junctions which are so congested that they cause delays at other junctions by the queues being back through the next junction (as reducing those queues can have a significant impact on delays).
24 (ish) people on a bus isn't a lot. When you're talking about trains (which often have over 120 seats) and the potential for reducing congestion is significant.
It's why those who like driving should actually favour government investment in public transport, at it would actually improve their journeys by car.
If you could pay to use a road which saved you 5 minutes each way each day for getting to work?
Whilst few car drivers would say £800 a year (£3.50 per day for 5 days a week of travel), that would be the total cost to run the UK rail network as it is (i.e. all £26bn) and not have any income. (hence my suggestion of a cat tax of £800 per year).
Yet an extra £31 per year (so about £1 per minute saved - which given the impact on a lot of car drivers of the rail strikes in longer journey times) would be the cost per car in the UK to provide an extra £1bn each year to run more bus and rail services. Given the large infrastructure maintenance costs, that would likely allow more than 1:52 (assuming half the money is for buses and half is for rail) more trains to run (and given we're talking about trying to maximise use of lines not running at capacity there shouldn't be as need for significant rail investment, however if there is that could be funded from the extra ticket income from those using the improved services).
You'd probably also need to look at running longer trains into major urban areas too so that the most cars benefited from the cost as well as increasing frequencies on lines with hourly service.
Actually by stopping all road building (including major improvements to junctions), you could potentially not have to pay any more in taxes than you already do. Unfortunately, the justification for public transport investment rarely can communicate these journey time savings to the wider population in a way which the people can relate.
Often they are an extra bus in their way, rather than the several cars which would otherwise be there instead. likewise they notice the minute at the bus stop and not the lower delays at the next junction (in that it's impossible to know about something you've not witnessed, i.e. how do you know what the delay would be if those 24 bus passengers were actually being transported in 20 cars without the buses not running or understanding how transport modelling works?).