"Many/most" is ambiguous. "Many" is 100% true, and having a different experience isn't any kind of a challenge to that.

Even if there's some question as to the theoretical legal enforceability of an agreement, if you have to sign it to have a job, then it's not practical to challenge it. You'd have to have the resources for litigation as well as to make a living after being blacklisted.

It is true that people ignore their agreements (about IP, not to run a side business, etc) when they think the company will never notice. That's still a meaningful risk that exists that some day they will.