(Not picking on
@Bletchleyite specifically! Plenty of posters have made similar points)
Fundamentally the issue is that it is done on the cheap. One more vehicle in the circuit and it would be far less unpleasant.
Of course, being part of the GTR franchise, GTR are running the service as a management contract, retaining no revenue and instead being paid by the Department for Transport to manage the operations. After the FCC rail services transferred over, and bus service operations were transferred to Go-Ahead London (in 2015), the buses were 10 years old, and got a refurbishment and re-livery, as is common for a mid-life bus. Given that plans for the DART would already have been known about, I don't think increased investment in the shuttle bus would have got approval from the Department.
I think the challenge - as with rail services - has been matching the increased demand at the airport to increased public transport provision, particularly off-peak. The Sunday mentioned above was the first after the lifting of COVID restrictions into the UK, resulting than increased passenger arrivals into Luton. Any decision by GTR to pay for increased frequency would likely have had to be referred to DfT, and of course the short notice of the COVID restriction announcement would have made it especially difficult for Go-Ahead London to drum up drivers to run the service.
There is an argument to say it surely can't be that hard to drum up just one bus and send a driver out... but as you say, these things are being done on the cheap, and the cheap doesn't pay to have spare drivers sitting about on a Sunday.
Why not just let the airport deal with it?
That's exactly what's happening -
@busesrusuk alluded to this - London Luton Airport Limited saw the opportunity years ago and is kicking in a decent chunk of the £225m for the DART, rather than spending money on new buses. The investment has taken time - the DART is key to the airport's multi-billion pound expansion plans, which have been in discussion for 2004. Trickling relatively small investment into the bus service wouldn't have made sense for an airport driving for massive expansion.
In truth, if you look at the web of discussion around the link at Luton, it really starts with the Network SouthEast development plans in 1989, following the runway improvements that year, that eventually led to the plans for the Dunstable busway. Those plans included the first proposal for a rail spur to the airport.
As ever, the simple problem of "this bus service isn't very good" is just one thread in a 30-odd year transport planning conversation. The bus link was perfectly fine (if not amazing) for 90% of running, but isn't up to the needs of an expanded Luton Airport, and would be approaching end-of-life very soon (in transport planning terms). Likewise, no-one has ever wanted to subsidise these buses' passengers, so it's always been darned expensive for what it is. The DART is a good solution, at a good price, and future-proofs the airport, the station, and the local transport network for growth.
I always tended to use the Arriva bus from the other side of the station instead, cheaper too.
Good commercial sense by the folks over at Arriva!
. Unfortunately I doubt that facility will be retained for the DART!
