I hadn't seen this until recently. It seems to be pushed by VCs and the tech megacorps, so if you work at a VC-backed startup it's likely in your contract or if you work for one of the bigger tech companies. I believe IBM had this for a long time. If you're working for a company outside of "pure tech", it's much rarer

Mega-corps have a) broader domains of "what's relevant" and b) more lawyers to actually take action on this stuff. Those are the only real differences. I've turned down jobs with even smaller companies over this.

I think it depends on how tech-focused your company is. Things like Google, Amazon and Bell Labs, sure, things like J.B Hunt and JG Wentworth (It's my patent and I want it NOW!) not so much.

Depending where you work in the US you may have not needed to sign anything because your employer already has that right by default. For example that is true in New York.

It will never get enforced unless there is some other conflict.