I mostly use cheating for unlocking content in game. Maybe I won't have a complete save file where I can use my favorite unlockable character, cheating remedies that. Or maybe for instance, i wanna use the badass Zero Suit option in Metroid Prime but don't have Fusion or a working GBA.
Some games are just stupid fun to cheat and play. Super Mario Sunshine is my favorite game to cheat in. I can play the whole game myself, 100% and all (plus all the blue coins), but sometimes I feel like sequence breaking or creating all kinds of stupid whacky antics for Mario to die of. Dat Moon jump code tho. Sometimes when you're too far up, you'll never come back down lol.