The granddaddy of the arranger, the home organ (with auto accompaniment) did not have a sustain pedal, and in fact, early single keyboard arrangers didn't have them either.

In any case, most arrangers are shipped without a pedal (including some TOTL) so it is basically an option...so, they must think that not everyone wants/needs a pedal.

Not every arranger player uses piano sounds as often as some others...those of us trained on the piano, or who were self taught on the instrument, need the sustain pedal. There are players who do not...lots of them...I do clinics and meet lots of players...I know of which I speak.