How and why do u throw a football so it spins about its long axis when traveling through the air?

How and why do you throw a football so that it spins about its long axis when traveling through the air ?
Rotational inertia

It's more aerodynamic that way, and as for throwing, you place your hand farther back on the football, lining up your fingers on the back laces.

For the same reason that gunsmiths rifle gun barrels. You want the rotational inertia to help guide the ball onto target. I believe that it helps to counteract the forces of drag, by causing the air to flow a certain way around the ball...