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.