My guess is that Bethesda made the number of marriageable NPCs in proportion to the races' population in Skyrim. Hence the overwhelming majority of Nords, large minority of Imperials, a few Bretons and Redguards, and a small smattering of elves.
This
Skyrim is the northern part of Tamriel and home of the Nords so you would expect most of people in the area to be Nord and thoses from nearby countries (Imperials, darks elfs etc.) It would be odd it was filled with Khajit who come from the opposite side of Tamriel, and were it's sub-tropical (snows cool but i'd rather live somewhere warmer)
oh and for people who are saying theres no Khajit in the game, I know atleast two named ones
Spoiler
one in the Mage college, can become a follower. another is an easter guy who says stuff about developers