There are some creators not uploading quality games on itch because
there is no easy DRM protection. If you ever wondered why an indie
developer wouldn't post a game on itch and would on steam, this is
probably a big consideration the developer went through. I've seen some developers doing what DireBoarGames mentioned as well, uploading the early access version but when the game is complete they are removing the game from itch. This kind of sucks for itch and its users and the developers.
I am sure I don't need to go on a long rant about DRM, but some of us developers would like an easy option for it whether it makes us friends or not :\