>>What, so people can jump the gun on the green, and slam into all the other people running the red light on the cross street?

No - the red and amber come on as the green on the cross street goes to red giving time for the cross traffic to get out the way before you jump the green.

A lot of junctions here do have cameras to get you if you are too early, so usually you just get your revs up to 5,000 or so and wait for the green to dump the clutch

I'm sure it reduces wear and tear on people's hearts. When I've been abroad and the light goes from red to green I'm like, "Whoa" and it's a bit of a shock. In the UK it's all pretty relaxing really.