The only real difference with most other car companies is that their different lines don't compete in the same exact space.
Nissan: Everyday cars, standard vehicle
Infiniti: Upscale/Luxury class for more affluent crowd
Toyota: Normal run of the mill cars, very bland
Scion: Lower-end vehicles marketed at younger buyers but with a tad of flair
Lexus: Premium car company, older/more affluent crowd
Honda: The most bland of bland for the average person who likes nothing exciting in their life
Acura: The odd quasi lux/sport cousin offshoot of Honda. Still haven't figured the appeal of these, way overpriced.
Ford: Normal American car for everyday needs
Lincoln: Does not overlap with Ford, starting quite a bit more expensive. Much more luxurious
My point being on these that pretty much no other company has 2 segments that compete on the exact same level like Kia/Hyundai does. Just seems odd to me. Maybe their line of thinking is twice the offerings then twice the sales rather than cannibalizing their own sales for the other?