Ask HN: Are non-solicitation clauses in contracts common and fair?

Hi all, I'm currently reviewing a contract I've received and noticed a 2 years non-solicitation clause in it. This is not the first time I notice this in a contract, and was wondering how common it is in eng contracts and if it makes sense at all to have one.

I never debated about it, and this is the first time I really stop to think about it.