Game creators have wide latitude to cancel games they create for any reason, because they have no opportunity to vet their opponent beforehand. For example, the game starts, they look at the opponent’s history and decide the opponent looks like a botter or an escaper (lots of timeouts in non-blitz), so they cancel.
By contrast, players who accept an open challenge see the specifications and can check out the opponent before accepting. These people are expected to play, and if they cancel a game you created, you can report them, and we will explain what is expected of them.
There are also cancellation trolls. This comparatively rare breed of troll enjoys wasting people’s time by canceling games. Coincidentally, a cancellation troll has recently been pestering OGS, so this is a timely subject.