The computer cheats

We have noticed that while playing games like the daily challenge in PvZ Heros, that there are several times that the game cheats. Is there a reason that it's set up to do that, because if so, then what's the point??? Is it doing that in hopes that no one notices that it's cheating or what's going on??? How can we say that we've played an honest game & played the best moves possible if the computer is allowed to cheat, I don't get it. Can someone please explain this???