Because it's dumb cap management, that's why.
Pollard is going to cost you. He's not going to be cheap. You already are going to take a $17 million cap hit for Elliott next year, which is downright preposterous for a RB. Now add in a decent cap hit for Pollard and you are looking at like $20 million + in cap charges for the TB position. Idiotic.
And there's only way this could get even worse. They could also restructure Elliott lowering his cap hit in 2023 but then ballooning cap hits down the road which would be ridiculous. The only way Elliott should be back is if he takes an actual pay cut. If not, see ya Zeke.