why do people hack?

Well some people just simply do it for satisfaction or just annoying others. Depends on the game really, there is a mobile game called "Last Day On Earth" and it's for iOS and Android devices and iOS users use hacks like free upgrades, duplicating items, free crafting and etc because on iOS you can save your progress on your GameCenter account, doesn't matter that the game files are modded. Android users can't.
So yeah that's one reason to hack I guess.