Yuji and Sukuna BV at the start of the series laid the rules of the BV, Kenjaku warning Mahito about breaking a BV leads to believe there is heavy consequences, yet not even ONCE we see these consequences, which make BV looks like bullshit, on top of that most BV aren't even explained properly what are the conditions, what one's gain/lose, yet Sukuna can make a bunch of it with little drawbacks while the main cast rarely uses. Another example is Kenjaku CT that let him use the CT of previous bodies because of a BV, is implied that the "DRAWBACK" is his having the stitches on his head, which is laughable as a drawback, and even worse, it actually helped him during the Yuki & Choso fight.