The answer is simple: It makes fans question the integrity of the officials. Especially in a sport that has a history of point shaving.
When the line is 9.5, and a player on the team with the 10 point lead has a player from the other team literally ON HIS BACK! and it is called a jump ball, not a foul, well, that makes fans question the legitimacy of the end results.
You may not think so, and that is fine, but you can't in good faith say that fans don't have a gripe. Especially in betting states. (Disclosure: I am not a bettor for any number of reasons, but if I were so inclined, what I have seen from NCAA refs would keep me from laying any money down on a basketball game.)