Because the return is much higher playing VP. It's called risk/reward. One could also invest in the stock market and accept higher risk and the potential for higher returns as well. VP is even better if you find the proper edge.
Go back and read LVA where I explained to you how much money can be made with a 2% edge. Just imagine how much Frank was making with an even larger edge.
In addition, I actually enjoy playing VP. I know Frank doesn't so even among APers there are differences.
For me it is based on how I feel. Win/loss is not even considered.