From a side scroller or platformer perspective this seems like a must have feature..... From a top down game, I can see issues where I wouldn't want things sliding along collisions.
Perhaps there is a barrel in front of the player. Now instead of hitting it, they might slide all around it. Despite a barell being a solid object you want a player to stop at. Or if an environment has objects or props rotated, now these become sliding obstacle courses.
Pushing objects at angles could now break and have players struggle to position themselves. The Boulder they were pushing is now a sliding wall and a nusance to the player.
Only a few examples, but I'm sure people could think of others.
Point being, it is a useful feature depending on the game. Aka specific uses.
Personally if something like that got added, a few of my projects would break. I would have to change over to custom movement which isn't a big deal, but defeats the purpose of an object that is meant to have basic functionality for us to then add on to for our specific games.
Also the 8 way movement is simpler in my net-code would hate to have it break haha.
Add too much, and it becomes the platformer movement. Great for that one purpose. Limiting for much else.