EDIT: I've just learned I was incorrect in my original comment below. Bars, taverns, nightclubs etc are included in third spaces according to Wikipedia. I guess I learned an alt definition at some point, or perhaps just a wrong definition.

The definition of a third place is that you can spend time there without the expectation of buying something. If you're expected to spend money to occupy space, it's not a third place.

(Fully agree that the loss of such spaces is killing us, though!)