Only because of taxpayers money and ensuring that all vital HMG depts are in the place. Your knowledge of this period is skant indeed. HMG cut one third of
the Merseyrail network; work started and was stopped, then proceeded to build a new 30 odd station metro on dock wasteland in London; not even in the centre. Manchester, Leeds, Bristol, Cardiff, Sheff, Notts, etc, can only dream of having such a metro. The Overground has been built and even a new underground station recently built between Kings X and St.Pancras. Then the Heathrow rail links and Crossrail at about £20 bn when all the costs are added up. The city airport, M25 and new terminals at Heathrow and now expansion of Heathrow. We can go on and on what they did from 1979 onwards in London while all others were stagnant.
Of course money should have been spent in London, it needed it, but not at such ridiculous levels and at the expense of others.