There's only a certain extent to which they can do that. If you're exploiting glitches that are common to the whole of Roblox and not just one specific game, then that's something they can deal with. But if a specific game has a certain exploit where you can clip through a wall or avoid damage or something or other (I played a lot of fast-paced action games), then that's for the person who made the game to deal with. If a server mod shuts down a player for exploiting a glitch that was only in one specific game, they run the risk of the person who created the game getting mad at them because it was a problem that could be dealt with while avoiding a perma-ban, which is bad. I choose to believe that Roblox's server admins choose not to deal with game-specific bugs or exploits because they want everyone to be happy.