i don't think most devs use this site to milk the fans, some of them do, like Dr Bones and ttll.
but if you look closely at your favorite abandoned VNs Patreon page, you will notes that most of them have something in common, which is not enough Financial support.
with it or against it, you can not deny that creating a VN is soul-sucking with or without help, and money is the only real motivation a dev can have to continue making his VN. If a dev is making $50 a month for at least 8 hrs of work in a day it's considered torture, it's no wonder why they decide to give up after 2 or 3 updates
their biggest mistake is that they're passionate and excited about making the best VN ever, so They rushfully jump on a big project without having any reputation or fans, so by the time their VN start getting attention and more people are showing up to support them, it's already too late. Their passion has worn out and they're already giving up. and probably never coming back.
The term "go big or go home" doesn't work here.