Aside from cheating, why do people use Stockfish? How do they use it for bettering their game?

You have already used stockfish when you used game review or analysis. While game review is nice, using analysis is better. Basically it is comparing the moves you made, or new moves that you think would be better, against what the engine (stockfish) thinks is best. Using an engine during a game is cheating, simply do not do that. There are many good openings and that is not what stockfish is used for, (IE: Play the Italian) openings are determined by you, not an engine. Just be aware that stockfish has its limitations because of the way it works, and thus is not the ultimate final word on a move. Overall it is a very good choice to use, and will help make you a better player. Stockfish (engines) does not ruin chess, it is simply an aid to help one to see further than they may be able to see at the present time on their own in my opinion.

They shouldn't lock it UNLESS people come and ruin it. Why not just delete their comments instead of locking?

Or just see what your mistakes were?
Yes.
The best course of action is to try to spot the mistakes yourself, then use the engine to check what you've missed and what you've miscalculated.
Grandmasters use them for other stuff too, but that's hardly relevant.

What does Stockfish say about Paul Morphy's games?
In the Opera game, from move 9 to the end of the game Morphy played the top engine move every time.

I don't have an account, but I understand that on this website you can look at every recorded OTB chess game ever played since the beginning of chess. ChessBase - Chess database with eight million games. Openings, players, tournaments.

Since the times of Gioachino Greco, in the 1600's. Gioachino Greco - Wikipedia

Chess enginers are good tools for training. One posibility is check with it your games after your first analysis. It is good idea to compare your thoughts during the game against the computer´s.Every time that you use one of this, try to understand the ideas behind the move.
Also is very interesting to check GMs famous games with computers, you will see the games are not perfect but they are beautiful.

I personally think its just for the analysis after they play the games. I don't use it and I don't know any people who do, but it's like game review in chess.com. I'm just assuming here, but i think its not to far from the truth.

reason people use stockfish in don't care what people say it's not cheating. Ur not good at the game if people has use stockfish every game they play then also have look it up ur not really good at it. In my life I never usecstockfish why because I'm real chess player by the real board and online. I'm 3 min blitz player. Got take long just make a move online then take 7 to 8 move ur not good. U should play easy game like games that doesn't need a brain.
I've never even searched for Stockfish, because I don't want to be tempted to ever cheat. But I keep hearing about Stockfish for analyzing games. How do people use it for this purpose? Try out an opening and memorize the best possibility? Or just see what your mistakes were? Do GMs use it to figure out new ideas? How has it changed chess? Let's start a conversation without discussing cheaters and getting the thread locked!