The problem with horses is they feel largely inconvenient. They can speed up travel time, especially early on when you don’t have fast travel access for the whole map. Horses: now a little less of an inconvenience to you! These mods will do just that by introducing new features or quality-of-life improvements to your game. For others, modding is a way to constantly add unique features to the game that enhance the experience in some way or another. For some people, the goal is adding more challenges to a game that is nearing its 10th birthday this year. Why do you mod Skyrim? There are no wrong answers and almost infinite choices.
With a game as old as Skyrim, mods that create a new experience are a breath of fresh air.