Perhaps it's the provision of heavy rail commuting that has facilitated the huge numbers of people forced to travel into such cities, often unnecessarily and inefficiently? Is it really necessary?
Do the large employers really need their head offices in city centres? Do employees really need to work in said offices? What about building offices in "out of town" locations? What about increasing working from home? What about using the internet instead of face to face meetings?
Similar with travellers - why should someone travelling from say Preston to Bournemouth "have to" travel via the "Euston, underground, Waterloo" pattern? Why are there no "hubs" outside major cities to deal with the "through" travellers that don't need to travel through the city? Why is there no rail version of the M25 so trains can go around London rather than into it?
Yes, I know changes like that will take years/decades to happen, but we have to start somewhere. As it is, we're blindly assuming that travel patterns of last century are still valid today. I.e. where people HAD to physically travel to work in factories, mills, offices etc (i.e. the London banks and solicitors where they "walked" cheques and legal documents from building to building which is now history). I.e. where travel took so long, travellers HAD to stop overnight on long journeys, so cities were the obviously place to stop due to proliferation of hotels etc.
With a long term strategy, I'd stick my neck out and say that you could probably halve the number of people travelling into cities and either change their travel patterns, move their working locations, or increase remote working. All it needs is the will and some long term planning from both government and employers. The existing system is creaking. If firms started to find it hard to recruit into the cities (due to high wage expectations to pay higher housing and travel costs or simply people not willing to commute into cities), they'd soon find alternative ways including remote working, regional offices, etc. The current heavy rail system makes it relatively easy and affordable to travel into cities, and as long as that remains the case, the situation will just get worse.