That means they're going to expect a lot of revenue. Which they plan to take on money that people give freely. I don't see that ending well.
I use Patreon on a lot, and I don't have any expectation that they are doing it for free. If they were doing it for free, then that would mean to me that the service would be unstable and would disappear some random month without recourse when its unpaid developer gets a job somewhere else, or someone files some light lawsuit against them and that's enough to take the whole thing down. A bigger problem than that they…
That's not really the criticism you're responding to though. It's not "People will be upset Patreon makes money", it is "people will be upset that Patreon will have to take SO MUCH MONEY from people giving it to others to justify their valuation."