There may be a number of reasons why a man is unwilling or unable to have sex. Viagra comes to mind. Men and women differ in many ways, both chemically and sexually, obviously. Their responses to sexual stimuli will vary greatly based on numerous factors. Men have a higher sex drive, and therefore will be aroused more, lust more and need more.
Studies show that men and women share sex drives of equal intensity.
Withdrawal is not an effective way to prevent pregnancy. Even before ejaculation, the penis leaks semen that can contain thousands of sperm that can cause pregnacy. Withdrawing after any amount of unprotected intercourse carries the same risk of pregnacy. A large penis is important for sexual enjoyment. Penis size does not determine the sexual enjoyment of either a male or his sexual partner in most cases.