I remember editing Privateer just for the heck of it.You are grossly over-generalizing. Once you are done playing a game normally, have exhausted all of the challenge and accomplishments you can out of it and are just plain bored with it, cheats, trainers, and whatnot can be fun to fool around with to extend the game's entertainment value for a little longer.
I was a huge fan of the original Privateer, way back in the ... i think 90's...and after a few hundred hours of playing it normally I started memory editing to modify ship parameters and got another hundred+ hours out of it. I'd have quit playing earlier if not for that additional gameplay that "cheating" opened up.
Yes, some gamers who cheat do so to bypass the challenge, and yes, for them they are cheating themselves...but it's over-generalization to say that is the case across the board.
That being said, in an online game where everything you do potentially impacts other players it is ethically wrong to use cheats and is against the ToS. And that's what this is about, whether it's "Fun" or not is beside the point.
I finished it 3 times without anything, but i loved the game, so I had a look at what's in it.
4 Steltek guns? Because why not!
Add a massive reactor to the tiniest ship? Because I can!
Some don't bypass the challenge, some just skip the grind because not everyone enjoys grinding.
In Mortal Kombat 10, you need coins to unlock the crypt chests - You can either play the game for 100s of hours, or just add coins and skip the grind, then play the game because you like it, not because you HAVE to play it to get the coins to unlock the chests.
You can just grind the coins on easy mode, play the towers on end and you'll get there eventually.