This one is quite a bit different. I agree with you
@Delta to a degree. I've played, in the past, on my Unreal Tournament 2k4 servers, and they had private ones where cheating, or hyper weapons, were allowed. However, that being said the private servers weren't hosted by Epic, Midway, or Atari. They were hosted by private players. In that retrospect, I think it's ok.
With Overwatch, all servers...even the ones against only bots...are hosted by Blizzard. Would be counter productive to host and run servers just to allow people to cheat on. And if everyone is cheating, then no one has fun. Other then the "private" bot matches, Overwatch doesn't have any single player at all. You can't even login to the game without having an internet connection.
No, when you buy a game like that, you never even own it. You buy the right to play on their servers and have to respect their Terms of Service accordingly. It's all borrowed time on someone else's expense. Same came be said with World of Warcraft. That one gets even more technical because if Blizzard finds out about private servers with that, they'll shut them down by suing the person that created the server. Letting anyone and everyone play their game without paying their monthly sub cost to it hits them hard.
Ultimately, when it comes to a FPS game, it really is no fun if people are cheating. You need a win sometimes to keep you interested in a game. If you're losing all the time, then the joy of playing slips out as well.