I have a theory that i think it is logical. I do't think anyone thought anything when it came to wrapping the ends of bass strings other than looks and easier on the fingers when use restring i guess. But my thing is I don't understand why you would at all. !st of all there is a wire to your bass bridge grounding your electronics to your strings for them to work. less contact is more noice in sound. So if the ball ends are wrap with thread it reduces metal contact to strings damping your ground causing more noice. And if your ends are wrap they are not making contact with your tuners also reduce the amount of metal mass that is more ground which reduces unwanted noice. This is my understnding on how the strings transfers sounds to the pickups. is because of the strings being grounded. So how or why did they start wrapping the string ends. I don't think anyone thought about this at all. My best hypothosis though but bet it can be scienctifically proven !