Put it this way: Everytime you don’t move left when you could, YOU’RE THE REASON THE ROAD NETWORK IN THIS COUNTRY DOESN’T WORK. You’re the reason that the motorways are always full. You’re the reason that people get frustrated and do silly things, causing accidents. You are the cause of the problem.
Undertaking wouldnt be be an issue if people drove properly. So next time you’re sat there in lane 2 or 3 (or 4!), and there’s room to move back left, then choose to be a decent driver and do it. Be the solution, not the problem.