Cos when its at 1 ohms its running balls to the wall wide open.
1200 watt amp, running 1200 watts at 1 ohm. At 2 ohms like 800 watts, 4 ohms 500 watts.
So, if you're running a 1200 watt amp at 500 like I am, its pushing the amp a lot less which makes for cleaner sound and cooler temperatures...