Have you played on a stage to make that claim? You're 100% making shit up to force you're narrative. I've played at massive BYOC LAN's in 1.6. You legit end up playing like over 20 maps in 2-3 days through practice and tournament games. BO5 is not a foreign concept, and teams have played them before without whining about an extra 2 hours of play time. The Grand Finals are always left for the last day of the event, which means there is more than enough time to do a bo5. Before it was 2 bo3s depending on the winners bracket, which was potentially a total of 6 games. We have also had teams play a bo3, right into 2x bo3 on the same day. Sorry if I don't feel pitty that some nerd is complaining about sitting on a computer moving his mouse around for an extra 2 hours. There is much tougher work out there in the real world.
Edit: The viewership is what pays the bills to these players, therefor it's pretty common sense to have the best ->viewer friendly/desired<- event
2nd edit: "by how smashed you’re feeling after 4 tight games.", guess games shouldn't be decided by how smashed a team is feeling after 2 OT's in soccer, or 4 tight sets in tennis, or 4 OT's in the basketball either. But they do, and not mention you need not look further than another e-sport game in DOTA2 where they hold bo5 finals in a much more exhausting game due to the fact you have less downtime, and have to go through a 20 min pick/ban phase each round.