I mean why would a steam user even buy your game there if he can just come here and get the game for free and on top of that get the newest version that hasn't even released there?
You do realize, devs generally don't account for piracy when it comes to tailoring benefits for their supporters, right? Or do you think they leak their own games in advance on purpose for some reason?
Also, in a perfect world, gentleman piracy would be the best thing when it comes to promoting a game IF it happened after STEAM/ITCH users got their release as well. But we don't live in perfect world. In-fact, most of the time, it's the one of the subscribestar/patreon supporters who just waltz in, throw money for a month and leak the game and continue to rinse and repeat with each cycle. I'm sure if the dev knew exactly who these leakers were, they'd refuse their money. But unfortunately, no one comes in with that kind of honesty stamped to their heads. The only thing they can do is to systematically release the game from the most expensive tier to the most affordable, so as to minimize the chance of a leak overtime.
In the end, if you choose to support a dev on STEAM/ITCH/JAST etc. by paying one time in advance for a WIP game, you need to make peace with the fact that the trade off is to wait. Early access is the biggest and most attractive benefit loyal supporters get to enjoy for their continuous backing of a project far beyond the price tag of a single copy.
Piracy is not part of the equation here at all and if you think that somehow taking your sale away from the dev is justified as you could just enjoy the game as a pirate, do realize that a hard working dev is sustained by monetary support. If it dwindles down, it won't be long before the "Abandoned" tag will adorn the pirate thread as well.
