In quite every culture, expect Western classical one, majority of musicians can also sing., for example, in minyo musicians sings playing shamisen, in Turkey there are saz player/singers, in Eastern Europe there are some epic tales storytellers who play/sing… so
1) Why this is not deeloped in Western culture, like there are not so many pianists who also sing, ecept pop
2) Particularly regarding minyo, in this case, but I can also generalize. There aren't off-tune people in the world, but some people are off-tune. For example, if I tell my mom to sing, she is terribly not able. But suppose that my mom is an excellent shamisen player, suppose in a sokyoku piece, and she has to sing. I think that majority of players (koto/shamisen/biwa/kin family) have to know/learn how to sing… what can they do if they can't for nature? Yeah, it's obvious that you can say that they can't as well… but… they just can't?
Yeah but… I just didn't explain. In sokyoku, for example, they sing… and they are mostly koto or shamisen players. I don't know also what's the melodeon