What part of a game you enjoy replaying do you dislike replaying?
I love the original Hotline Miami but I'm not a big fan of the boss fights like the ones in Neighbors (Biker) and Deadline (Van Driver). I find it kind of slows down the game and limits the strategies you can take.
Another example would be Fallout 3. I find the tutorial section in Vault 101 can feel a bit long after a fifth run but maybe that's because I was spoiled by Fallout New Vegas' ability to run off in your own direction immediately after leaving Doc Mitchell's house.
Maybe but some people don't use mods like that because they disable achievements but there's mods to re-enable them.
Could also be that they don't know about them. I feel like they aren't super popular. A majority of the time they just dump you somewhere with some loot and you still need to backtrack a bit.