I really don’t understand why bighit isn’t h…

I really don’t understand why bighit isn’t hiring any better vocal coaches for bts? Like they’re arguably one of the biggest musical acts currently, with fantastic rappers and dancers, and then the singers are just… really not that good? I’m geniuenly not trying to shade the vocal line, but they haven’t improved much if at all, and if they had actually been taught by good coaches they could become pretty decent singers. why are they blocked from making progress that would benefit them?