Of course it would break things. It would break bookmarks that use the node title. And I'd bet there are quite a few of those. It could be made to not break bookmarks, and perhaps that would be better... it might even be easier...
But the reason nothing has been done is more that it is a non-trivial amount of work and once enough time had passed for people to register complaints, I had lost the burning desire to fix it and now it seems unimportant compared to other items that I'm also not able to find the time to do. ):
