maybe you should say which piece this is
i always thought (and i could be wrong) that if the notes were comfortably in one's hand - then you finger sustain and add a bit of pedal later
i never only considered it for tone. in fact, to say that it's only purpose is that seems to be stretching the truth
i think the real truth is that not many teachers or students use the sustain pedal and they don't really know how it works
just experiment at home and find the sounds that make the piece to your liking (but practice as your teacher says to gain flexibility with your choices)