Some of that is because the camber of the road (ok, some roads more than others) makes every start a minor hill-start. By applying the handbrake you should be preventing any chances of rolling into the kerb.
I was told to keep it in gear with my foot on the clutch. Now I only do that if I know the cycle time is quite short, otherwise it goes into neutral and the handbrake goes on. I don't impede traffic because I see when the other lights change and am back into first before my light goes green.
Another point is that I hate fecking bright brake lights in my eyes and I am courteous to those that might be stopped behind me.