Jump to 8:45 for an illustration of the previous statement. Ride like that in the first lap scrum and it won’t end well. Even a two-up last lap against a non-teammate probably wouldn’t be so physical.
But with teammates (at least, teammates who like each other) there’s little risk of a seriously dangerous move or creating a lasting grudge. Even if one rider ends up on the deck, the squad still wins, and no one comes across as a villain.
And you have to admit, it makes for a pretty great show.