Why BTS members have never promoted as a subunit?

what is stopping them from making one officially?

it doesn't have to be between the most popular members. it can be a rapper + vocalist etc. They have many options, why they never do it?

It's been years since they've been doing group activities let them enjoy solos. But Hybe once did say that they'll do solo activities maybe we'll get JK x some rapper or jimin?

because they didn't promote anything other than the group?

They would be too powerful

When would they have had time?

because of akgaes maybe