It’s a consequence of our capitalist society, of how we’re not allowed to just exist in most places without buying or consuming something. About the only places we have left are sidewalks, public parks, libraries, maybe a large mall. Anywhere else and you can potentially be asked to leave if you’re not seen “doing” something or at least looking like you’re going to buy something after awhile. If the staff don’t care, you can “get away with it” (that is, get away with just existing), but more often than not you may be asked to leave. I’d try to test the theory out by just standing around for a few hours, but who actually has that kind of time?