Oh, replace Y with why, it makes a little more sense.
I think the question is 'Why must violin music only be played on violin when it sounds just as good on other instruments?'
Baroque violin music was, by and large, also for oboe, recorder, horn etc. etc. The concept was known as 'absolute music' - the instruments used were rather irrelevant. So one gets Bach concerti for two violins, or violin and oboe.
After the Baroque period, though, music started being written with specific instruments in mind - taking account of string crossing on string instruments, register crossing on wind instruments, etc. Of course, if you enjoy playing violin music on recorder, go ahead, there's nothing wrong with it

. Piers Adams certainly does a good job of it

.