If the music is worth being accepted into consciousness, then performances must match the music. It shouldn't be tossed at us without the necessary polished presentation. It can't just be good enough to get through the notes with the appropriate speed and dynamics. It must be music, with all the intricacies and expressiveness that only a real artist can bring out.
Speaking as someone who has given a few premieres (of works by composers living and dead), I would say there is more of a 'moral imperative' to give a good performance of new/unknown repertoire, simply because if I play, for instance, Beethoven badly I look like a fool, whereas if I play Denis ApIvor badly I risk making him, not me, look like the fool.
Hey J Menz, what works have you premiered?