It’s pretty common for artists to vault some of their favorite music because it doesn’t fit a project or because they can’t get a sample cleared
Most the greats create trash more constantly than greatness and have great quality control
Unless u are Miles davis or somethin its imperative to vault most of ur work
Which is why Jay-Z removed Ghetto Techno from Youtube
That’s why I miss the mixtape era.
Everyone wants to make as much $$ as they can and I get that so they’ll vault songs with samples that are too expensive to clear. Some songs don’t fit the overall concept of the album and for some of these artists that drop once every 2-3 years they just save their music for albums and only want what fits that ‘sound’.
Like some people posted, I think a lot of artists will recycle verses or at least some lyrics from vaulted tracks.
Everyone probably got their own reasons tho