I mean, keep disagreeing with Joe Silva, in his own words, describing how he has tried to drive down a fighter's market value when they fight out their contract.
"I lowballed them on purpose the first offer knowing they would turn it down,” wrote Silva. “How bout I come back with 29+29, 32+32, 35+35, 38+38. If they turn it down I put him in a prelim against a really tough guy for his last fight.”
In his deposition Silva was asked about this tactic of giving a fighter a “really tough guy” for their final fight, if they have refused to re-up with the UFC. Talking about the Diaz situation, Silva said he would have given Diaz a “tough guy regardless”, but conceded that he was more likely to give a fighter who re-upped a slot on a main card versus a fighter who was fighting out their contract."
Uhhh..Ali Act came after most of those guys retired, and it was never meant to prevent brain damage. Nice non-sequitur.
Those reasons are for losing a fight (most fighters lose one at some point) and breaching the Code of Conduct, which the UFC enforces and doesn't enforce at its own whimsy. So the reasons a UFC fighter can be cut are quite broad and more or less whatever the UFC wants.