English is virtually the only language with a complex word for "yes." Think of how you have to pronounce it. You have to make that smiling lip motion to pronounce the "ye," then you clench your teeth and hiss to make the "s" sound.
Spanish - "cee."
Russian - "da."
German - "ja."
Japanese - "hoy."
Ebonics - "yo."
All of that can be pronounced instantly. It can easily be spat out repeatedly. Yes, yes, yes. Da-da-da. Ja-ja-ja. Hoy-hoy-hoy (a bit more difficult but Japanese is weird anyways). And we all know how fluid "yo yo yo my brother" flows from one's lips.
I say we change "yes" to "ya" and burn all the old dictionaries.