Let me explain PvP in a very simple way

[Absurdity]

Ya'll are forgetting the most frequent variant (as pertains to Frontlines specifically):

Team A plays well (or more likely gets lucky) and takes an early lead.
Team B and C then spend the entire rest of the game tunneling Team A, both disregarding the map's objectives and failing to notice at any point both of them have long since overtaken Team A's score.
Team B and C continue doing this until the end of the match, thereby needlessly dragging it out through their own lack of situational awareness.
Team A meanwhile has been locked in a cycle of gaining and losing people since the moment B and C put them on the back foot.

Or Team C notices so while A and B keep duking it out and tunneling hard they silently overtake both.