For the same reason Artemis Crock didn't start out with one of her aliases on this show, he started out simply as Mal Duncan before his other hero aliases in the comics.
Originally Posted by Gold Starz
His voice and how it sounds seems to be a voice directing choice by Jamie Thompson. I remember when Eric Lopez voiced Mark Allen (Molten Man) on Spectacular Spider-Man and he didn't sound annoying or stereo-typical. So I'm not sure what it is they're going for with this Blue Beetle, but I agree in how it has come across as annoying.
18. Blue Beetle-- We'll talk when you get a new VA. Pun Intended.
"Don't cry over spilled milk, get angry and punch a cow!"