Native Londoner here. I wouldn't move:
Diversity, interesting people from all cultures plus amazing food from everywhere on my doorstep. I'm from a minority background and not had any issues.
I can walk to interesting places, or walk to the tube and be anywhere in central London within 30min. Never drive. Feels like freedom.
Sense of history. Layers and generations of different people, archaeology, mudlarking, Romans and Tower of London and Dickens and... All adjacent to shiny modern architecture.
Most good jobs in my industry are here, plus I can go to all the events and conferences and then be home in 20min. I can go to a school play and back to work. Admittedly I live relatively centrally.
Culture and arts. I do regularly go to exhibitions and take my kids too. I can walk to both Tates in 45min, and I have three small local theatres within a 20 min walk plus Leicester Square theatreland close by tube.
South bank wanders, river and the city at night, general atmosphere.
No wild countryside which is a downside, but we have parks, the heath, Richmond and Kew.
Friends from out of London come and stay!