Every single time

And sometimes that dumbass is you

It does. One idiot braking as they change lanes/switching to a lane without indicating and forcing someone behind them to brake. Then another idiot brakes and forces his way into another lane, forcing that lane to brake. Eventually everyone has to stop simply because enough idiots think switching lanes is a great idea to get out of a traffic jam. Stay in your lane unless you need to switch, it'll go faster if you have patience.

In my country, if there's a traffic light/enforcer then there will be a traffic jam. The flow of traffic is much faster without them.