Don't get me wrong, I hate steam because it inevitably will be a problem after some amount of years.
On the hytale side though, they literally aren't on steam for the reason in a recent news article on their site:
This doesn't mean Hytale will never be on Steam; right now, we don't see the need for it, as we want to keep our launch closer to our community. It’s important to note that Steam currently doesn’t support some of our modding features; we will be in contact with Valve in the near future to see what’s possible.
Reading between the lines, with the emphasis i've added... the "modding features" they don't support are paid mods. They want that creator club / roblox experience ASAP.