This might be a silly question, but why is it that pianists (sometimes) get a page turner, whereas violinists, cellists etc. turn their pages by themselves? A violinist too can have both hands busy, so what accounts for the difference?
This is particularly noticeable in (though by no means limited to) piano trios: there are four people on the stage - pianist, violinist, cellist, and the pianist's page turner. Why is it that only the pianist needs a page turner, while the others do not?