This is true I guess. I haven't seen their contract. I've never had an issue with any noncompetes in my contracts though. I can see why you wouldn't want to employ and train people in your business only for them to go to a direct competitor. I think that's fair, you just need to look for a good job in an unrelated business.

If a company wants me to not work in my field after I leave them, they can pay me for the condition. At a multiple of going market rates.

The reason people can work for the competition is that they're not slaves. There are few businesses Amazon doesn't compete with (all of retail, books, publishing, tech).

If they want their workers to stay, make the prospect attractive.