I'm fairly sure it doesn't takes all that time for me (at PC). But i'd never took the time to check it.
Well, maybe some people don't need to work at all, have you ever thought about that? It was already mentioned i'm sure, and it wouldn't surprise me that the same people, with the same lifestyle are playing over and over again...
Anyway, it's not important to me what others do with their time, you included, if you want to start a crusade based solely on suspicions you can always ask the developers to check the top ten players.
Maybe there is something weird about the leaderboards, maybe a botting/cheat system undetected (so far).
Or maybe you are wrong because you can't imagine yourself doing the same ammount of battles and then you assume that they must be cheating because you can't compete in the same terms; same ammount of free time, willingness to spend this time playing and experience*.
*Experience being accounted as being used to recognize some patterns of gems, moves and troops that must be destroyed first to finish the battle faster.