I have a theory!
I propose that there actually is no such thing as a right-handed, or left-handed, violin (or guitar, or whatever) because it actually has NOTHING to do with the right hand performing the 'more difficult' task of bowing, etc., as has been the reason most often stated.
I propose that the reason we bow (or strum) with the right hand is because it's easier to attend to OTHER TASKS with our dominant hand while we are holding our instrument.
"What other tasks?" you ask. Well...good questions! Tasks right-handed people do automatically with their right-hand, without thinking about it, such as:
Shaking hands.
Marking the score.
Turning the page.
Scratching.
Holding a cup of tea or a frappuccino.
Shooing away flies.
Etc.
It's just easier to put down a bow or a pick, than it is to put down the instrument, and we are thusly much more likely to WANT to hold on to it for safety reasons.
Since this was never an issue with the piano, that's why no one ever talks about 'left-handed' pianos.
Yup.