I've noticed that too. I can't say why but people seem to turn their noses up at these names. I know two lovely, polite Kaydens and one lovely Cai. I also know a Kye who's a nightmare. A nightmare Christopher too!
I noticed this when I was pregnant the first time and teaching a difficult group of boys. Lots of names beginning with k/c. Coincidence probably but all those names were off our list because I didn't want to name a child after naughty boy I'd taught. Didn't need to worry as we had a girl!