> average people just don't care much about anything, especially quality.
That's incredibly arrogant, and more than a little naive. The problem is that you're only looking at the small part of the problem which you understand better than the average person. Think about it instead from the perspective of the ice cream shop owner: they're not making any money from your using the network.
You might look at the a Facebook captive portal and think it's a poor choice but your solution isn't optimized for the business needs: cheap, reliable, doesn't require much staff time to support or special skills.
This particular problem is really a tech industry market failure, as there's never been a serious attempt to build a federated authentication system because the general trend has been trying to force a closed system on the world with the goal of levying a tax later. The most successful attempt was OpenID which was fundamentally mis-designed – inexplicably using URLs instead of email addresses – and quickly derailed by the gratuitous complexity crowd. There's a chance we might see things change with Persona but … I'm going to go out on a limb and guess that this won't happen quickly and, even if it does, it's going to be hard to find many developers willing to turn down a Facebook-scale salary to work on a turn-key level captive portal system priced at what an ice-cream shop can afford to pay.