Well, first off, “free” is not a requirement for a 3rd place

in order to be effective it has to be. there's plenty of places where you can go out if you can regularly spend $10^2 or $10^3 on a weekly basis, but not that many people can, hence the problem. we need to set out with free as an explicit requirement or we will fail.

back when I went to college I tried handing out in bars, but it was too loud in all the ones in town but one that was too far from home to hear yourself think let along have a casual conversation, and the drinks were too expensive to make it affordable. eventually I decided drinking at home was cheaper and stopped bothering. lots of fast food places are starting to explicitly post time limits and even in places where they don't I feel pressured to constantly consume or leave. I've never timed how long you can sit there before being formally asked to leave for loitering but a business wants to free up space for paying customers so the pressure exists which makes any private for profit business a poor choice