Assuming gloves give better traction
the gloves have sticky tack on them to make things stick to them, if the qb wore gloves it would make it impossible to throw properly. some qbs wear gloves on their non-throwing hand
When throwing a football, small differences in the finger and hand movements can impact the ball’s trajectory a lot. Especially with the pros, there’s a very tight window of opportunity when throwing a pass, so quarterbacks want the best feel for the ball.
Most of the QB’s that wear gloves usually have smaller hands so the gloves give them a better grip on the ball and less likely to drop it.
Receivers wear gloves to keep the ball securely in their hands. A QBs job is to get the ball out of their hands.
When throwing, you have a better feel for the ball and more control when not wearing a glove. WRs use them because they increase grip and make it much easier to catch the ball and they help hold onto to it once you possess it, but when throwing, grip is less important than feel/control.