There's a few possibilities.
1. To enhance people's view of themselves in juxtaposition to such obvious losers.
2. Some of the libertarian concepts and ideas are so compelling that there needs to be an opposing side and even the obvious losers provide that service. That speaks more about the lack of value in the other political parties than the losers themselves. I mean, if there's an imbalance that requires keeping even the most obvious losers on board perhaps the balance that's being sought is out of kilter. Harboring obvious losers is not conducive to attaining the best -- it hinders it.