@typhlosion Some of it, surely, is simplicity. RS-232, or at least its low-voltage variant, is much simpler to use than USB. You don't require any sort of impedance matching or specialized integrated circuits.
@typhlosion I managed to completely skip over the word "simplicity", apparently.
@typhlosion Well, now I'm embarrassed. Sorry about that!
@Rosemary grao it's ok
@Rosemary did... you read the whole post? i said that i understood it in rs232's case and even specifically mentioned its simplicity