I can't understand why any male would want to shave his armpits. For whatever reason, I never developed armpit hear until I was in my 40's, and even then just thin, short hair. This is despite the fact that the rest of my body is extremely hairy, and has been since high school. People would constantly ask me "Why the hell do you shave your pits?" I would answer that I don't, but I think that they often didn't believe me. I always felt that I was missing something because I had so little armpit hair, and people's reactions tended to confirm this feeling.
In fact, armpit hair serves an important sexual function, and even among women, the practice of shaving is declining. The hair traps the pheromones secreted by axillary glands, and acts as a wick to make these important chemical messengers perfuse the air during sex. For more information on the function of axillary hair, and the history of shaving it, see:
Underarm hair - Wikipedia, the free encyclopedia