Because if it’s pre-recorded then wouldn’t it be interesting if it’s exclusively released as a movie in theaters? Blackpink The movie on theaters was basically the show (the it’s not exclusive obviously) and it was 10xs better experience to see the stages on theaters than home.
This also would lessen the leak. Obviously it’s not something many groups can do because the theaters aren’t going to take every group’s concert lol but if someone started it, they can.