Probably because people are more comfortable with traditional Men and Mer fanatsy races found in fanatsy films, games, and novels. This is probabaly the case Elder Scrolls veteran or no.
Also Khajiit, Argonian and Imperial racial abilities are terrible, and for Khajiit in particular, embarresing compared to the extremely powerful/useful abailities of the Orc, Redguard, and High Elf races.
In adition, I imagine stealth characters are the least played types, while Mage and Warrior are clearly defined and lend themselves with more realism to the other races in terms of abilities, physical appearence, story, and once again normality in the sense of traditional fantasy.
That being said, even though I rarely play them, I enjoy really the look of the Khajiit. But a Khajiit and Argonian Dragonborn? Yeah sorry I don't see that at all.
This has to be the DUMBEST comment ive seen in awhile. Firsst of all Khajiit, Argonian, and Imperial races are very popular. And their abilities are'nt terrible. Khajiit and Argonians are the best for Theif/Assassin Characters which are popular with players. And if You actually pay attention to the Story Line there isnt a "race" that all Dragonborns are. Any Race could be One. You sound like an idiot.