I think that, unless you are London born and bred, therefore your roots and support network are there, the perceived advantages of London over other big UK cities are far outweighed by the huge disadvantage of the cost of housing.
Only the very very wealthy can afford satisfactory housing in London, whereas in Leeds, Birmingham, Manchester, Newcastle, Sheffield, Nottingham, Bristol etc almost everyone except the very poorest can afford appropriate sized housing in decent areas and we have just about everything else London has to offer, except the big national sites (Houses of Parliament, Buckingham Palace, Tower of London etc) but that can be easily sorted with a weekend break, should we wish to visit.
If we want museums, galleries, open spaces, countryside, restaurants, culture, architecture, diversity, sporting events, music, and everything else, that some Londoners seem to think doesn't exist outside the capital, we have it all on our doorstep for whenever we want.