Sometimes they are not bred because the time and money spent in breeding does not make sense when wild caught/imported individuals can be bought very inexpensively.

I have a Green Ameiva that I won during a trivia contest at a herp show. He's cute and will eat out of my hand. I don't think I would have bought one, and think they have a very small following because of their flightiness. But he's fun to watch and I made him a nice habitat. He's like a little tegu to me.

I thought Chilean dwarf tegus were lizard eaters and that put them out of favor with breeders as being high maintenance. I'm not speaking from experience, though, only hearsay.