I dunno maybe ethics, morals, respect for those who pay... just sayin'...
imo, the real issue lies within the very Patreon "scheme". All the (valid) points you're making only hold up if there's a super clear
buyer/seller agreement. And on Patreon, that's often just not the case. It's more like "I'm the artist/creator, and you're basically supporting me so that I can keep making stuff". This very principle alone doesn't actually clarifies
how much content said artist/creator has to churn out, nor
when he has to deliver it. We should prolly start thinking of it as a tip-jar, indeed. You toss a coin or two their way for the beer you just had, but this won't necessarily mean that a beer on the house is coming up next.