Like you stated in your previous post: "safety in numbers". Plus there's so many around that drivers are probably accustomed to it.

I think local driving habits plays a part too. In my town I'd consider splitting lanes and jumping a red light to be quite risky as plenty of motorists run red lights and/or fail to signal lane changes and turns. On the other hand rolling through stop signs is becoming almost expected. I don't know how many times cars basically waited for me to roll through a stop sign and then be surprised I actually stop since they had the right of way.