This is not true in trading. If I go take my strategy/forecast and go to a competitor, I can just outright take the same opportunities that the other desk was taking (to a fairly good approximation). There's no real branding/network effect - it's a pure quality of execution business.
Furthermore the industry attracts the sort of people who are never satisfied with what they got, and are always looking for more.
Not that I'm advocating for non-competes, just saying that you can't address the concerns non-competes are attempting to address by "paying employees well".
There's definitely an argument here that those companies deserve to be out-competed then.
I'm not saying to ban any of these practices, but the legal system doesn't have to guarantee the feasibility of companies.