It's one of those old lines men trot out around other men. They exclaim that sex is their "biological imperative" to free themselves of responsibility for their desires. It's a get out of jail free card for being a reprobate.
We evolved to have an entire hierarchy of needs. These folks use those big brains of theirs (that we evolved to continue developing as children independent of our mothers specifically because we evolved to have these conversations) to obsess over sex, and to ascribe their value to that. That's their choice. But the rest of us have ascribed our value, our existence, and our legacy to mean many and varied things independent of reproductive capability.
My advice; don't try to understand things that will only make your worldview smaller.