Why do men have big tesitcals?

Answer 1

Wikipedia says:

Testosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid. In men, testosterone plays a key role in health and well-being as well as preventing osteoporosis. On average, an adult human male body produces about forty to sixty times more testosterone than an adult human female body, but females are, from a behavioral perspective (rather than from an anatomical or biological perspective), more sensitive to the hormone.[1] However, the overall ranges for male and female are very wide, such that the ranges actually overlap at the low end and high end respectively. In general, androgens promote protein synthesis and growth of those tissues with androgen receptors. Testosterone effects can be classified as virilizing and anabolic, although the distinction is somewhat artificial, as many of the effects can be considered both. * Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of linear growth and bone maturation. * Androgenic effects include maturation of the sex organs, particularly the penis and the formation of the scrotum in unborn children, and after birth (usually at puberty) a deepening of the voice, growth of the beard and axillary hair. Many of these fall into the category of male secondary sex characteristics.

Answer 2

When a male is born, their parents get to decide on the overall growth of his testicals, as is the same with the male penis. So if you have small testicals it's because your parents don't love you.