Originally? Probably lack of options. These days the aim of the game is sounding “like a violin”, so naturally there’s very little innovation in violin technology.
You literally asked a question and got answers… Seems like you found one?
Violinist here.
Violins make sound by dragging the bow (stretched horse hair) over a string, causing the string to vibrate. At the micro level, the bow pulls the string to one side using friction, until the tension on the string pulls it back - this happens hundreds of times per second, and forms the basis of the sound we hear. Horse hair is slippery by default. To create the necessary tension violinists apply a small amount of solidified tree resin by wiping a piece along the length of the bow. This piece of hardened resin has the same approximate texture as glass or hard candy, and is called rosin.
Oh, it wasn’t bought… It was bough
Took me a while to realise they weren’t asking about the B.A.T.M.A.N networking protocol on some sort of “T??? Attached Storage” device