>>101746289 (OP)You're talking about holofes, correct?
It's not about bringing everyone together; they mostly do that every year anyway.
It's the fact that doing it live would require so much more singing and dance practice for each holo to memorize all the choreography and vocals for 4+ songs. It would mean that everyone would have to go to Japan 3-4 weeks ahead of time so that they all could learn their choreography to a level that would be good enough to perform live. And they wouldn't have any extra time to stream.
Also, it's really hard to dance and sing at the same time. Many of the members that aren't performance-inclined might not even be able to do that.
And then there's the risk of technical malfunctions. The tickets are already expensive and the plane tickets for overseas fans even more so. Cover isn't going to risk anything going wrong during their biggest event of the year. That's why holofes will never be performed live.