The footballs used in college games have white stripes at the ends. The footballs used in professional games don’t have stripes.
What in the Wide Wide World of Sports is going on with that?
My WAG would be they’re intended to help field goal kickers and receivers. Again, just a WAG.
My WAG is so the person tuning in can tell immediately whether it’s pro or college. 
And if it’s not pro, switch stations. 
Here’s another WAG…
Quite a few high school and college games are played at night, sometimes under less than perfect conditions.
Not so for the pros, who usually play during the day or in a stadium flush with floodlights.
Maybe the lines are so the young 'uns can see the ball better when the lack of proper light might be an issue.
And why aren’t the stripes full circles? I think they used to be full circles, but now the stripes are just half circles. I think the rotation of the ball made the full circles look cooler than the half ones do.
What’s the reason for the stripes only being half-circles?
We’ve been here before:
http://boards.straightdope.com/sdmb/showthread.php?threadid=42559
From a Wilson Sporting Goods FAQ that I dug up for the earlier thread.
Thanks. I should have known that so elemental a question had been answered already.
Here’s WAG #3 (only since the prev seemed to possibly have some validity to it…)
By eliminating the full circle around the ball, you can more easily judge the amount of rotation around it’s long axis. If I see a ball with little rotation, I know it’s not going to carry as far as one with a lot of spin would, especially against any kind of a wind and, therefore, I need to make adjustments to where I think it will come down. Also, a fast spinning ball needs to be caught with a little more dexterity than one turning slowly.
In my mind, the circles are for the direct benefit of the receivers.
In the 1940s and 1950s, football teams would sometimes employ white footballs with black stripes to make it easier to see the ball.
You mean before color TV? 