Or maybe they're just not as good as they fancy themselves (except Lanipator, that motherfucker has range and should imo already be getting Christopher Sabat's roles after Sabat's "casting couch" antics were outed, but double standards and so forth).
For reference, Kira Buckland worked in at least one abridged series, plus innumerable Newgrounds projects... yet she was the main character in one of the biggest games of recent years. Regardless of one's opinions of her, the girl had the cojones (and probably luck) to grind, slowly getting roles until she made it.
Maybe they should have seen the writing on the wall and, once Namek got finished, put an actual effort into being noticed on their merits, maybe do a couple reels, do bit parts in some bean mouth CN show, and build a resume... instead of illegally riding Dragon Ball's coattails.