Most places with wifi around me don't offer great options. My local school blocks a lot (and I'm mostly there outside of school hours, they block more) - these are mostly places I wouldn't go anyway, but once in a while I hit something blocked. My office does the same - but they don't have public WiFi, an employee needs to get you a login (this is easy to do, but if you don't know someone who works in the building you can't connect at all). Most public wiki (including school above) also requires you accept a terms of use. Most devices won't automatically connect to any found open access point, so to use public WiFi I need to manually do everything.

That is I don't think people will use WiFi only, unless they are going to drop always reachable communication. (which given the SPAM OP mentioned maybe...)