Companies probably like people moving from the middle of nowhere to SF or London better though. Especially young kids will probably undervalue themselves. They may know or figure out that you gotta ask for more salary in those areas but they might not know how much exactly they need to ask for and/or go down too much when HR starts their spiel.

Hopefully they've learned enough about how much the company values them and how much it cares about them, that they don't just accept a relocation and whatever salary their company gives them. I'm not too hopeful though, given what working conditions they already accept while living in SF (or wherever).