Why do PE...DUH!!! It's so I have a reason to play with my dick all day.
Seriously, initially, it was insecurities, I wanted to boost my ego, self-esteem, and confidence when I was naked in front of women.
At first, PE was a struggle, it was overwhelmingly confusing, monetarily extortionate, time consuming, and the gains didn't exists as easily as I originally thought should happen. I wanted it just as much as the other guy sitting quietly in his bedroom thinking about it. Along the way, I learned the hard lessons and gained more and more PE knowledge.
One of the most important lessons I learned from PE-training was. If you really want to succeed at something time-consuming and difficult. You can't simply dabble in it, you have to learn to master it. Now, the main reason to do PE, is for the sexual health benefits of keeping in shape for doing sexercises with a training partner(s).