> There's also the fact that there's a lot less social pressure for young people not to look stupid.

Also also they tend to be less financially "tethered" for want of a better word - mortgages, families, children, etc. - which makes it easier for them to be risky (consciously or not) about what/who/where they work on/with.

Probably not likely to be jumping from your stable 9/5 to a startup when you've got your semi-detached with 4 kids.