Well we only have $200,000,000,000 in reserves to pull from. Not tithing!
We use it for malls, rodeo grounds, property, investments into big pharma, etc… I don’t see why the Church chooses not to support their own school’s athletic programs which in turn is the life blood for all the other sports programs at BYU? It’s also the second most visible and identifiable entity for the Church if it’s important to get the LDS name out there. Opens doors for Missionary work probably better than almost any other asset the Church owns.