Because in S&

you get 2,500 xp per turn (then you switch and your partner puts on his riot shield).
So, Player 1 shoots player 2's shield and gives him 5 ticks of 500xp, then player 2 does it to player 1, and back and forth.
But in sabotage you will only get like 5 ticks of 100xp, so 500 xp per turn.
My record is 119k in 1 S&

match (7 rounds)