You're usually not party to a non-solicitation agreement in which others are not allowed to solicit you. If you as an individual contractor sign such an agreement with your client, your client's employees whom you're not allowed to solicit were not party to the agreement.

Even if you somehow forced everyone to be part of the agreement, it's irrelevant - whether Apple's and Google's employment contracts had language that forced the employees to agree to what's going on here is not exactly relevant consideration.

Edit: part of the irony of this whole "non-solicitation agreements are illegal" chorus is that I think most people complaining probably have signed such agreements in the past as they are quite routine. Granted, most of the time, it's just handed to us and we have to sign or gtfo.