I don't know how prevalent this is becoming outside of Chicago, but here there is NewClub, which is somewhat vetted* membership society that runs some events and similar programs. They have tee times at some local private courses for a guest fee that you can book through the society (though maintain some standing times at public courses as well). You do everything through the app is my understanding. Point being, at least in this area (and I believe in Atlanta as well), there are private courses that are making times available to a segment of non-members I would imagine as a way to increase revenue, and possibly showcase the club to prospective members.
This is my first year checking it out, so I'm not sure how frequently these times are offered, and clearly I'm not accessing Chicago Golf or Shoreacres via this society (though there are some highly thought of clubs in the program). Presumably this is another way to generate revenue, but it also gives the clubs an opportunity to limit access to a group of people who a) had to go through some sort of examination process before being accepted into the society, and b) probably have an incentive to avoid getting kicked out of the society. So they aren't just opening things up to the local riff-raff (theoretically).
*I mean, I filled out a pretty long application and was invited to write a check. A fair amount of effort was put into to creating the application, but no idea how much effort was put into reviewing it.