Actually there is little thinking about "Amazon" or other competitor: internal mobility is easy. So replace "Amazon" by "this other team is doing a cool new project", and you can get transferred in a matter of weeks, most of the time without going through a heavy interview process.

And all of this isn't only motivated by "not doing boring tasks", but also because this is what drives promotions / career advancement. So "launch a feature/project, get rewarded, and switch team" seems like a trend, and it does not encourage to think about long term maintenance / etc. (It isn't a generality either, but it is a bit of a trend)