Blatant cheating to troll is one (myg0t "clan" is the first notorious case I remember from back in the day).
Another is "cheating" to fix problems in the game. Some games are really good except for a couple of issues. An example from back in the day is Final Fantasy XI. They programmed it so ALT-TAB would crash the game. They thought this would stop cheaters (Japanese devs don't seem to really get the PC landscape sometimes) but it was just really inconvenient for the rest of us. I hit it by mistake/habit more than once in a tense moment. So a third party hack called Windower was invented to stop this.
Predictably, it was very popular but there were also players saying those who used it were dirty cheats who deserved a ban. Alsod predictably, because it already operated in a grey area, it received a number of QoL updates and features including add-on support and scripting where anyone could easily develop things that clearly crosses the line.
Looking back there was a lot of tedium in Everquest. Tradeskills. Attunement. AA points. Traveling was a pain in the first few expansions. I don't deny that I was cheating, but certain types of cheating can reveal flaws in the fundamentals of the game.
The original game designer Brad McQuaid (RIP) defended that tedium, particularly around things like travel, as necessary to give you a feeling of achievement. He was also worried about inflation in the economy. Although I have some warm memories of playing EQ I vehemently disagree with his views on game mechanics. In retrospect I realize I enjoyed his art style more than anything. I plan to give the follow on Pantheon a miss because it too plays to the poopsockers of the world.
If it was up to me, entering the Konami code would unlock everything in every single player game. Everyone has the right to access content they've purchased in the way and order they see fit.
But when you're playing with other people there's really no excuse.
Consider games like WoW. Ask anyone what the game is like, and you'll find that the game "doesn't really begin" until you are already max level. That is, the "real" content of the game is all of the Guild-related activities. Everything up to that point is more or less an extended tutorial that lasts for dozens of hours.
Cheating because you want to skip the "tutorial" and quickly get to the point where you can play at the same level as your friends seems like a perfectly reasonable goal. In fact, now a days I believe WoW provides a free (high) level character for all new players, but for a long time, you needed to run through that grind yourself, or pay a microtransaction to skip up.
What I do in fact fundamentally not understand is why games are designed this way†. Good on WoW for apparently letting players skip it nowadays. I admit, I'd have trouble faulting someone who wanted to cheat their way through.
† Outside of games that explicitly want to sell micro-transactions. I understand that all to well.
Some like the rush of doing something "naughty".
Some want quick results.
Some want prestige.
Some want to explore and exploit the system itself rather than the game.
Some want to gold farm.
Some want to be like gods.
Some want to automate the tedious parts.
Some want to take down big mobs that can't be taken down any other way.
I once wrote about 400k of Blech code for Macroquest to automate the most tedious parts of EQ grinding, and to automate support party members (running on separate accounts) when I couldn't find a group (before the mercenary system), powerlevel new accounts, or needed more precision to one-group multibox raid targets (for example, Overlord Mata Muram). In many ways it brought the game to a whole new level of challenges due to the difficulty of my targets, and the strategies I needed to employ.
It was actually quite cool, consisting of modules for healing, buffing, offtanking, main tanking, positioning, dd, dots, aggro management, clickies, AA abilities, timers... the works. I had a configuration language that assembled the necessary modules to produce the behavior I needed for a particular task.
All of the dev work involved, at my professional rate, would have come out to 5 or 6 figures, so there's that :P