Online broadcasts.

Actually, streaming is useful for those who want to learn something. It compensates for waters, etc.

That's true. But almost everyone who wanted to has already learned :) If only it were 5 years ago.

In tournaments, it's of course unpleasant if an opponent joins in, but in a group of three there's no such problem, because the game is purely based on trust and the opponent's conscience, since you can reveal the map or cheat by any means.

There are some tools against cheaters, however. Besides, the maps are well-trodden, the final layouts are known, and strong and fast power-leveling jumps out at you.

As for friendly games, the benefit is of course undeniable. There is, however, one problem - Time. By watching saves, you can learn practically everything with minimal time investment. The point isn't about how to kill a specific monster at an object with a certain army by watching a video and learning. The point is how to be able to complete a certain set of tasks under any layout and get to your opponent faster. You'd have to watch too many streams to learn that :)