Run enough RBGs and you will win some games by default.
I found if there were more than 2 players not ready, a ten man RBG would often just skip the game.
In the limited number that I ran, we almost always met 10 and occasionally 9, but basically never 8 or fewer.
But we did have maybe 1 in 12 games, where the opposition just did not show up.

That's basically the same with doing Arena too.
Or at least it was, when I played.