I have seen a few and they look pretty good, maybe the problem is that by the time you get to the desert earlier pets are at quite a high level. It can be a pain to lose out on that for a new lvl 5 lizard...
That's true. When I got to the desert, my wolf was about Level 13. It was tough parting with the wolf for a low level 5 dune lizard. But I did and just power level the lizard to level 20 by killing griffons and minotaurs.
You just aren't playing in the right location. I have been doing alot of pet/barrage groups in the Tombs UW and I get at least 1 ranger with a Lizard in every group. I think they are actually pretty popular.
I think the problem is that people just dont wanna level up their pet again, so they either stick to the Stalker they got in the ranger quest, the wolf they got in shiverpeaks, or wait to get the underworld spider.
Lizards are convenient to get, however, for people who switch their secondary to Ranger after reaching the desert and are too lazy to go back to Ascalon for the Melandru's Stalkers roaming around.