#3 UFC is not offering Lesnar enough to interest him
While Lesnar has enough money to not need to fight, it is also the truth, that given Lesnar's outlook on life, he would never turn down a lucrative deal if it seemed right for him.
While UFC is the most successful company in the field of Mixed Martial Arts, it is difficult for them to match the demands that Lesnar possibly makes.
On top of that, Lesnar knows that if he accepts a contract with UFC for a fight against Daniel Cormier and actually wins the UFC Heavyweight Championship, he would need to defend the title again.
Lesnar has revealed before that he is only interested in facing Daniel Cormier in the UFC, and the prospect of later having to face other fighters if he is able to defeat Daniel Cormier does not appeal to him.