Well, while many people keep ball pythons as pets, not many people keep them long enough to fully realize how dietary choices ultimately affect these snakes.
In other words, there may be long term consequences to feeding a snake who eats several different prey items just one item. I've seen it in boomslangs and other dispholidines that I've kept until they become senior citizens. Same with some other colubrids. They develop some debilitating health problems as they age.
The behavior in males is deliberate - not necessarily casual. I'd have to re-read the papers as to the behavioral or biological necessity that drive avian predation.