Some people (that are done with a character) want an excuse to use that character for day to day play vs being routed onto an alt. If SSG let any TR/ER I did on my total completionist main be assignable to an alt, that'd be a big win for me; I could play my main and still have a way to pass along progression.
That's a good idea. I would like to see it. But....It ain't happening, cuz many people would use their main to get past lifes on their alts quicker than they could if playing said alt. They will never allow for that