having an adbreak right when the most important play of the game is made would really be annoying. It's not like broadcast tv where there are things like time slots and designated ad spots.
That's why Twitch gives you tons of tools to schedule ads and manually trigger them at less disruptive times. It requires the streamer to care about not disrupting their stream enough to plan ahead and preemptively run ads and not just hope they auto-run at the right time.
This very seldom happens to actual competitive events (which often have special deals that require them to run less ads), and most bigger streamers have worked out running ads between games.
