Answer: To start with, let's not mislead any impressionable readers that may be in the room: it isn't actually correct to say that most scales start on C. But I think I know where you're coming from here - "C" has a big and seemingly undeserved reputation among musical pitches. One might ask, "Why not A? If we've decided to name the notes A,B,C,D,E,F,G why is it that we hear so much about C??"

The answer is that that the most familiar melodies use the major scale: whole step, whole step, half step, whole step, whole step, whole step, half step. And that is the pattern of steps outlined by the white keys of the piano if you start on C. Naturally the C major scale is therefore the first one everyone learns. And "middle C" is the pitch exactly between the treble and bass clefs used in piano music. "C" is famous.

But the major scale can start on any note. By using the black keys placed there for just this purpose you can play that same pattern of whole and half steps beginning on C#, or Eb, or any other. So really, C major is just one of the many transpositions of the major scale, and its only real distinction is that it is played without using any of the piano's black keys. On the violin it has no special status at all.