The sibling posters have covered it, but the stop-and-go phone driver already has greatly reduced situational awareness because they missed out on the 3-5 seconds of events before the light turns green.

When I'm stopped at a light, I will check my rear view and side mirrors just for any cyclists, motorcyclists splitting lanes, or even for distracted drivers who might rear end me. I may pull forward a few extra inches to let the occasional car behind me make their right turn. Drivers focused on their phones can't extend this courtesy.