Now You Know (Source)
Is that why ancient Greek statues are all lacking in that area?
Classicist to the rescue! Short answer: yes. Long answer: It’s a bit more complicated than that, of course.
The reason we see so many statues that look like this (naked, buff, not-well-endowed guy looks into distance) is because it’s a trope that’s come up several times in Western art history. Most recently, the Renaissance and Neoclassical periods saw it used heavily because it emulated the statues done in ancient Rome. Those statues in turn were emulating an ideal that (some of) the Greeks, particularly after about 500 BCE, held.
This aesthetic goes hand in hand with several others in Greece — one of which was the athletes’ nudity in the Olympic games — intended to show off the (young, buff) male form. It’s considered by Classicists who study Greek art history to actually be a homosexual ideal, particularly that of the eromenos, or “beloved”, younger member in a male homosexual partnership, who was typically in his teens (hence why these statues are not bearded) and not yet (heterosexually) married. In sexual relations, he was expected to be (what we today would refer to as) the bottom, and thus emphasis was not placed on his genitals by sculptors and artists of the time. The other male aesthetic ideal, that of the erastes (“lover”), was typically older, bearded — think of all the bearded guys you see on Greek pottery — and (almost always) clothed.
(The association of big dicks with barbarians was derived from the fact that non-Greek men were not believed to conform to the erastes/eromenos relationship ideal, rather being more interested in heterosexual sex no matter their age.)
No wonder Xena chose Gabrielle.