Patreon and other similar sites promote lazyness. People support games theyd like to see finished and while without support the devs are trying their best, after they gain funding they realize they can start working on a "per hour" basis and earn a living by never finishing a game.
Not gonna throw accusations around on who is guilty of that. I will buy the game once its done and would never spend a dime prior to that. You buy a product, not a resource.
i'd go ahead and argue it isn't the site itself, that promotes lazyness. As a lot of times, when it comes to corporate misbehavior of some sort (think of EA and their DLC policy, Nestlé and their moral decisions, Apple not paying taxes, etc.) they get away with it, because the appropriate people simply do not care. And the appropriate people to care for patreon scams are, of course, their patrons.
There are a lot of patreon accounts out there, that did deliver small demos here and there, but nothing major. Still, they have been collecting thousands, sometimes tens of thousands
every single month. For
years. But their patrons still stick with it. They are throwing their money away, and apparently, are fine with it. Patreon can't really stop them from doing so, therefore i do not see any fault on their side.