I was asked to sign one once, I said no, and it turned out the startup had just got some standard contracts from someone and was using them because they had them, not because of some specific concern so they had no problem changing them to something mutually acceptable. Any company that won't do this is not worth working with.
It’s fine. Just make sure the scope is as narrow as possible. At my company, I signed one. But, before I did that I found 5 other companies that I would want to work at someday that are tangential to us and ran them by the founders for clearance.
My policy is that I don't sign a noncompete for anyone. They serve no legitimate purpose. In at least a few US states, they aren't even legal. If you're in one of those, then it's a bit of a nonissue.