There's no reason a server couldn't be set up to have UOp and HOp.
Even if they couldn't it would be completely confusing if ishop worked with uops aswell since they usually have completely different access levels. So any code made to work with hops and the common access given to hops would then trigger for uops which the scripter most likely never intended, causing the code to break.
I also don't see the need for an isuop operator, otherwise why not support any other half-assed usertype that IRCd developers decide they want to throw at people? Using $nick() is a much more adaptable method than the is* operators.
