So why do people want low kill times

The original Halo was dominated by the pistol that killed in 3 shots. 2 body shots, 1 headshot. That game's sniper rifle was truly a fast semiautomatic rifle with 0 recoil, could kill in one 1 shot and 2 at the most. The rocket launcher instantly killed anything it exploded next to. As for the other Halo games, they revolved around controlling the power weapon spawns, all of which could wipe an entire team out in a handful of seconds. The sword was a 1 hit kill on anything. The plasma pistol locked onto players like a heat seeking missile and took half their health and didn't even need to be aimed directly at a player. The battle rifle had the advantage of gigantic player hit boxes, including a huge critical hit area on the head. The shotgun had a huge one hit kill area, shoot them in the foot and their dead. The tanks killed in 1 hit. The ghost ran people over. The banshee had a bomb that instakilled players.

People died in Halo very, very quickly.