Driver making a left on a green light usually assumes that the cross traffic has a red. So generally no reason to look right when making a left at a light.

But... I live in Texas and in the last two years I've seen three 60+ MPH double T-bones on legal left turns (double because the driver running the red still has their foot on the accelerator when crashing, so "Smash, Screech, Smash" again). So I look right even when turning left at a light. Every time. Without fail.