Regarding your point about notice periods in the UK, that's not really a given. More senior people typically work as consultants and it is not uncommon to have

Regarding your point about notice periods in the UK, that's not really a given. More senior people typically work as consultants and it is not uncommon to have a zero day notice period. Which works great for both sides - senior people don't have issues with finding jobs and if the job turns out to be a chore they can do 'kthxbye' and be at a new one the next day. This is the same for workers doing work through an agency which gets increasingly more popular. Notice periods can also by asymmetrical - the employer can let go of the worker without notice period, but worker if they want to quit need to give 2-8+ weeks.