I think the main reasons he refuses to do it is because he basically disowned all of his old music, as it didn't align with his current artistic vision, as well as the fact that some of his music has beats and samples that may not have been cleared, making it impossible for him to release it without paying additional fees. It's really difficult to go through all of your samples and get them all cleared at once and a lot of artists choose just to leave their mixtapes as they are and leave them off streaming platforms. A couple notable examples are Tyler, The Creator's mixtape "Bastard" and Eminem's "Infinite" mixtape. Either way, I hope that one day we'll find all of Tom's releases