Because it is a global capital city. In this context, London's transport is not nearly as good as it ought to be, and many complaints are justified. That does not mean that public transport in the provinces isn't also poor.
No, all the squabbling is all the usual zero-sum mentality which is one of the major cultural drawbacks of this country when politicians pay attention to it.
I look at the lack of Leeds Trams and the reluctance to build Crossrail 2 as well as the reluctance to build new infrastructure all across the country as apart of the same cause, it's all the same problem. London area may be at a higher level but it's still held back from its full potential, given its size. England is way too centralised in the hands of Westminster, especially DFT and HM Treasury.
We really need a federal country where each region can fund its own projects, borrow, raise taxes and levies like we see with Nottingham's workplace parking levy which funds their trams and buses. We are going through local government reorganisation at the moment, so all areas of the country will have unitaries, combined authorities and mayors, seemingly within the next 2 years. With that and devolution, I wonder what's the point if they can't all raise their own taxes for their own priorities? Priorities that mayors will ultimately get elected on, like Tracy Brabin promising trams for Leeds and Bradford or Kim McGuiness promising the reopening of the Leamside Line to Metro operations. Things they should be able to easily do without relying on a reluctant Westminster who can't see the value in such things. Same with the Bakerloo Line extension in London or the nearby Lower Thames Crossing.
I find it really inappropriate that any major project, something like a new bridge/ tunnel or tram or metro system, what are essentially city and regional projects are left to a final say in our national Parliament. It seems so far from what reality should be. Parliament should be able to focus on national and international issues while most internal issues are left to local and regional politicians, people who are a lot more accountable in their towns, cities and regions.
Even with London, it should never have had to resort to begging the government for money to keep things running! The sheer wealth in the city, especially from services, real estate and construction, it should be able to build anything it's mayor and residents deem we need for our future regional prosperity. Something like the Freedom Pass should never have been in question in the first place as it's really an admin expense.