I will only speak for myself. I cheat a lot in single player games, and hell, I'll tell you why.
My basic philosophy of gaming is that it's to entertain me. If I leave frustrated and pissed, then that's bad news.
So let's say I start a game. I see a game with a list of stats and a lot of numbers and I get a level up for skill points. I think to myself, "well this is okay, but I really want that skill and I don't want to wait", then I bust open artmoney and start adding things, all the while thinking to myself "it won't be that easy. In fact, it probably just helps a little. There'll still be a challenge". More likely than not, I end up being wrong, and the game loses a lot of the challenge and I realize I kicked myself in the back by ruining the experience.
I add money cheats because I'm impatient and I don't want to grind, and though I cheat with skillpoints, I'm more likely to cheat with money because I find it relatively harmless. In most games, money will not dramatically wreck the difficulty curve. For example, Lara Croft and the Guardian of Light requires that I rack up over 1,000,000 experience requiring several playthroughs to unlock a costume, so I just artmoney it and I'm good. I never use god cheats/one-hit kill cheats because it will just too obviously kill the game. I don't cheat in puzzle games like Trine or Portal or other games with no RPG elements because it's just pointless. I don't cheat in online games because someone else loses out in a competitive match (it's not victimless and it's not fair), but I would be willing to cheat if it's cooperative vs environment.
I just have difficulty controlling my impulses enough to work for it, even if I know cheating will kind of ruin the experience for me.
Oh,and I edit my characters with feats because I want to make the perfect character, and unfortunately the perfect character requires more badassery than legally allowed.
Honestly I agree 100%. Single players games are fine in my eyes.. I'm not ruining anyone elses experience. It's fun to modify your own character and be super beast.
When it comes to online gaming, I don't cheat often. Like mentioned before, If I find a glitch, I will indeed exploit the hell out of it. It's not the gamers fault. It's the programmers fault for letting it slip. We could go round n round about this discussion. But it basically boils down to is.. you either A) do it and like it, or B) you hate it and want to kill people for doing it.