Actually this started with BH and Kiswe in September, the other two are just joining now. It is probably motivated by huge costs of hosting that kind of events by third parties like Youtube. Some of you were mad at me about my comment about that YG group concert... well as you can see they dropped YT as soon as possible.
I think it's just agreement between YG&BH , BH also invest in YG's project.
something like if I do this you will do that in return etc.