Surely the main reason is that there are plenty of public transport alternatives - either alternative rail routes (for Central London) or service buses which are more frequent and not much slower (if at all, door to door).
So I agree that blanket ticket acceptance on local buses would make good sense.
I can quote another bizarre anomaly re Southern's current withdrawal of through weekday evening rail services to Horsham via Epsom and Dorking after the 1725 service from London Bridge (that would normally depart from London Victoria) that has been ongoing since January 3rd.
So from Jan 3rd to Jan 21st Southern simply left those of us using Holmwood, Ockley and Warnham stations with no way to get home other than a taxi (albeit that for about an hour after 6pm there was an alternative option from Dorking on the violently expensive and pitifully slow -35 minutes instead of 10 minutes on the train - Metrobus 93 service not covered by your rail ticket). But then on either Monday 24th or Tuesday 25th Jan Southern laid on a Rail Replacement Bus starting from Epsom and running all the way through to Horsham and stopping all all other stations along the way (the one man self bus owning rail replacement bus guy told me he lived in Pulborough some miles south of Horsham on the A29).
Unsurprisingly I thought Southern had listened to my posts about no weekday evening services from Dorking to Horsham in this forum and had put this Rail Replacement bus on so that passengers from London Victoria could use it from Epsom (where trains then terminated) while passengers from London Bridge could pick it up at Dorking. So I used the last of three hourly rail replacement buses in the late evening for my journey back from Weymouth to Ockley on Tuesday 25th Jan and then also used it on Thursday 27th Jan after going to London for the evening.
Believing this to now be a permanent fixture until normal train services resumed south of Dorking in the evening on a weekday I went up to London on Friday 28th Jan for another event and then at the restaurant I was at just checked my phone to check services were running normally only to see to my horror no rail replacement bus listed. Thought this must be a timetable mistake so debated between getting the train from London Waterloo to Leatherhead where Uber service is available or carrying on to Dorking where annoyingly it isn't (although I now know you can get an Uber from Boxhill & Westhumble as its still in Uber summoning range of Ubers circulating in Leatherhead, Ashtead etc). But as Dorking is always manned by a station supervisor until the last train (whereas Leatherhead isn't and has no one there at that time of night) I decided to go to Dorking expecting that I would be able to get the station supervisor to call a taxi on Southern's taxi account since it was clearly illogical for the Rail Replacement Bus to suddenl disappear when Dorking to Horsham evening services had not resumed. And this is a Rail Replacement Bus with an actual point as it saves a significant taxi fare and moreover the rail replacement bus passes within 0.3 miles of my home compared to 0.8 miles for Ockley Station and the rail replacement drivers are always quite happy to drop me off as it saves them going out of their way to Ockley Station (a set down only stop).
Anyway got to Dorking but the Station Supervisor said no there wasn't a rail replacement bus today and it had been taken off as the rail works it covered were finished. So I then ask why that bus had run all the way to Horsham as though it was covering the missing evening rail services south of Dorking. He said he didn't know and seemed in a bad mood as he was having to kick three or four drunks off the terminating train at Dorking who have overslept their stops. So anyway after he had got rid of them I kept talking to him about why there was a replacement bus for three days and now nothing and told him a Dorking taxi rank taxi at this time of night for the 7 miles to Capel was around £40 due to 50% surcharge after 11pm. Finally seemed to win him over with my knowledge of the line and history of the train services and as he was going home to somewhere south of Three Bridges he agreed to drive me back down the A24 to my home and then cut across country to his home. Initially said he wanted something for petrol money but by the time we had talked about the rail services in the area and his job he said he didn't want any money for the petrol when we got to my home.
Subsequently I have discovered that by walking around 1 mile north of Dorking Station that an Uber can be summoned from Boxhill & Westhumble Station so I did that one night the next week coming back on the last train from North Camp to Dorking Deepdene and a couple of other nights I got off the train from London Waterloo to Dorking at Boxhill and successfully summoned an Uber for only just £9 compared to the normal £16 due to a special 40% off Promo running that week that had a maximum discount of £7 on a journey (so basically perfect for a journey of this length achieving near maximum percentage discount). Sadly this week the promo has ended and it is cheaper to go back to totally unmanned Ifield from London (if I meet a ticket inspector en route I think can pretty reasonably argue I am en route to Horsham as a legitimate routing point to Ockley station and the nearest station with still running train service at that time of night) where the regular non discounted Uber fare for the 7 miles is between £12 and £13. By contrast a licensed taxi from the rank at Three Bridges station after 11.30pm would be around £37.50!
But anyway this was a Rail Replacement Bus with a point and each night there was another passenger (not the same one) travelling on it with me but now Southern have withdrawn it with no explanation as to why they put it on in the first place on Jan 24th or 25th and then withdrew it after Jan 27th.
But this is a bit like asking Southern why they are now showing trains south of Dorking from London Victoria from Feb 20th onwards but with a last train at 2122 rather than the preceding last train before the Omicron service cuts at 2325. The staff working for the Teleperformance run Southern contact centre have no idea why and if you ask for a proper explanation in writing you are told you will get one but as with all of the four complaints I have logged with the Southern Contact Centre in the last four months no written reply is ever received. So the only solution with that is going to be escalate these complaints to the Rail Ombudsman.............