Here is the answer.
Why big dick.
1. Our satisfaction.
Lets talk about biology of orgasms.
1. Clitoral orgasm. We all know what is it. It is mostly achieved by oral sex or by hand. Very rare that a man can give by penis. And for circumcised to give such an orgasm by penis very very very difficult.
2. Vaginal orgasm.
This kind of female orgasm begins in the vagina and either stays focused in the pelvic and lower stomach areas, or spreads from there. The uterus, pelvic muscles, and even anus may begin to contract during this orgasm. Those contractions are quite strong and may actually push out anything that was stimulating the vagina. This kind of orgasm takes longer to achieve (it takes a woman on average 20-25 mins to achieve this kind of orgasm) Rhythmic thrusting is often the best way to get her there, a good lover will communicate with his woman and find out the best position for her to reach it.
How does this kind of orgasm feel to a woman ?
Many women describe it as “less intense” than a clitoral orgasm, but more deeply felt. They feel it as a pressure that slowly grows and explodes deep inside the vagina. This varies greatly from woman to woman.