For the artists before this, I think it's because they're confident they can develop another catalog. So if your backlog isn't performing as well anymore and you can make maximum profit, while not, instead of dedicating time, money and resources to generate more money for it? Dream, Bieber, and John Legend aren't retiring anytime soon and for two of them, a lot of their work is behind the scenes anyways. Bieber hasn't even hit his adult r&b phase while still showing his brand is strong and viable. A resurgence for him wouldn't be surprising.
The lump sum is taxed lower than the general revenue and I may be wrong, but you also still have the ability to rerecord if you want.
Ye is entirely different situation and selling his shyt up front would be best for him bc he'll never see a bunch of money from his music because every song has 4+ writers, expensive samples which credits all of those singers and producers as writers, etc. His music is just generally expensive overall bc of how much he collaborates. Which is why he was trying to get so much money up front for each album and it increased as he released albums (according to the contracts he released). Him selling is cashing out and wiping his hands free of that
Not to mention, he also lost billions of dollars and is still presumably fighting, not only an adidas/GAP lawsuit, but also multiple settlements for damn near everything now from Donda 2 samples (he released commercially without clearing, antisemitism/sexism/etc settlements, not paying studios/mixers/masters)
Him selling his contract shouldn't be indicative of anything more than him needing money considering how much his old stuff still gets used in media