On one hand, yeah, no one makes you give to a Patreon account, or continue giving. If one feels that the person they're giving patronage to isn't continuing to produce work of/at a consistency level that made you want to support them in the first place, withdrawing is certainly the patron's right.
On the other hand... There's certainly an odd psychological feedback loop where people, having invested something (time, money, effort, a vote...) in something (a person, product, campaign, cause)... Feel a need to continue investing in that thing, and finding ways to justify the expense. So do bad politicians continue to have careers, wars continue to waste lives and resources, and a billion fandom arguments continue to rage. We seem to have a switch that would sooner have us throw good money after bad than admit that the original expense was squandered and we would be better off admitting the mistake and moving on.
I hope that if I ever have a Patreon account, I can continually offer something of value to my patrons... But if I'm honest, part of that would probably have to come from taking a hard look at how much time and effort I can realistically put into those offerings in a month at a rate that I could reliably maintain. It's easy to believe that you'll always produce work at the level of quality and frequency that comes of the early days of a project, when you're full of enthusiasm and the very idea of getting paid for doing what you love is novel and exciting. It's quite another to continue working at that level when it becomes... work.