I think...probably... and this is just an observation, but because a lot of the games on itch that advertise future release to Steam offer a steam code to those who bought the game here when it launches on steam... Maybe "most" is unfair I've only seen a couple games advertise that but I think some people have come to expect that to an extent.
Really love what you got so far definitely was worth the 10 bucks, cant wait to see it develop further! keep on keepin on!