There are intellectual property assignment agreements though. These basically say "we're a giant tech company and work in a lot of areas, so if you work on a side project in any of those areas, we can assert rights over it cause it competes with us and you probably stole that knowledge from us, or thought about it on work time, or something".

>and most of the best paying tech companies have decent vacation policies

You get 15 days at Google for the first 5 years (even if you come in with experience). I'm not really impressed by this. I will probably never see 20 days of vacation from Google. Cisco had 20 for everyone. Other companies may vary.

>Lots of people have hobbies other than coding

This is not the case for me. I play some video games and I write code. I like programming more because it feels productive, games are fun though.

>Is it really that hard to imagine that people might be willing to make fairly minor sacrifices in exchange for several hundred thousand dollars a year?

It's not hard to imagine that (it's how I ended up where I am), but now that I'm in the situation I don't really like it.