Most fantasy lizard peeps have breasts because it's the easiest way to portray to most people that they're females. There's plenty of other ways to show this, but boobs are the most direct method that humans identify with instantly.
STOP TALKING ABOUT LIZARD T I T S AND MAKING SO MUCH SENSE! No lizard boob discussion should ever make sense. Anyway, I just had a thing in mind where a lizard chick would attempt to seduce a human, and I wanted to know for that reason, I'm deciding against lizard boobs because I can think if a couple funny scenes where that would come up.