Because your five dollars gets you nothing. For five dollars you're getting access to one update, older versions if the download links are still active and you want them for whatever reason, and you can read any posts made for the rest of this month. You're not buying the game, and this isn't a Kickstarter situation where higher tiers can grant you a copy of the finished product. You're paying a guy five dollars for THIS copy of the game. You will need to pay five more dollars for every update right up until the dev drops off the face of the earth at version 0.47 or wherever, or until the end of time as the development continues on for years and years. That means if you choose to support this dev completely the final cost of the game could be hundreds of dollars and you're unlikely to ever get a completed product.
In all my years following porn games I've supported dozens of devs to varying degrees, and only ONE ever went out of their way to send me a download link to an updated version of the game even after I stopped giving them money, as a thank you for the twenty bucks or whatever I gave them previously.
The standards among Patreon porn game devs are rock bottom. These people are not professionals, and they don't treat their games professionally. Most of them don't engage with their game's community to any meaningful degree, many don't make consistent or detailed posts outlining what they're working on or when the next update should be due, their game's updates vary wildly in quality, there's usually a shockingly little amount of new content per update even from creators that make thousands every month. Many developers actually slow development as the size of their support base increases, probably because they realize that finishing their game would probably be the worst thing they could do since it could jeopardize their money by forcing them to create something new that might not bring in the same level of cash. I could go on, but I really don't need to because everybody is well aware of how much Patreon sucks ass as a platform for game development.
This is not worth five dollars. 90% of developers deserve to get their games uploaded here. Sorry, but I'm not sorry.