Why people still talk about Lergo in this day and age is beyond me. Irrelevant side character who got negged by Law. There's nothing more to him.
The same reason they talk about Doffy or Lucci or Enel or anyone else. They like those characters so they won't shut up about them.
Me and you may think he's a painfully bland and run of the mill villain that has nothing to offer whatsoever, but they think he's cool, tough and nonchalant. And like everyone else on this site, they think that in order to like a character, they need that character to be absurdly strong. Which is why they wank him to high heavens.
No difference from a Shanks fan coping that he's above Mihawk even though Shanks' character doesn't even depend on him being stronger or weaker than Mihawk. They just feel insecure if a character they like is weaker than they seem.