If a team decides to go out third, they basically lose 1 point to the 2nd place team and 3 points to the 1st place team. It's better to tryhard and get the points before split 2 so you can save more strats and have more prep time before champs.
In AM it's basically just wheather or not NRG can win masters AND the split to overtake Sen, but in all the other regions it's still likely that you can overtake your peak team for the free slot. I mean, KC lost today - Navi and Fut have a huge opportunity to overtake them.
Btw I'm saying this with the ideology that if a team has the free champs slot 100% locked up, they'll kinda stop caring about split 2 so they can be their peak for champs.