Earlier quoted context omitted.
I really can't understand why they stay in the UK then, to be honest. We seem to have better salaries and generally lower cost of living across the sea... I have no affiliation with this company but here's a recent example, quoted at 95k so you could presumably push higher: https://www.ninedots.io/job/lead-react-engineer/
Family, friends, football club, being in ones own culture? Not everyone is ready, able or willing to start a new life somewhere. And an important detail to remember is that Europeans usually work a lot less than Americans. Due to progressive taxes people tend to choose for more time off rather than more pay.
Yep, anecdotal but time is just so much more valuable in my 20s than the extra (taxed) money. The sweet spot atleast for me is a 3 day work week. Pays enough and it has a decent balance.
I could never trade this situation for a US dev job even for 3-4x the salary.