Why do people like doctor or lawyers chose to live and practice in places that are aren't very nice?

there are a lot of towns and cities in Britain (naming no names) and I would presume america that well not very nice places to live I.E low in come, high levels crime and antisocial behaviour, presumably if you visit one of these places and got ill you would presumably go and visit a GP (general physician) and he logically as a lot of towns are very far away from any where else (even in some parts of Britain) he must logically live in the town.... why would any one who's gone though several years university and now makes �80,000 an year voluntarily chose to live in some where horrible? why don't they go and find some where nicer to practice and bring up their family?