When I was younger I had a similar attitude, but I changed my tune as I got older. The idea is that it makes the roads overall more efficient thus benefitting society. I leave for work 2 hours before my shift starts and I usually get there 30 mins early, but I always leave 2 hours early anyways because it only takes 1 guy driving slow in the left lane to delay me and hundreds of other people 30 mins and it happens about once every 2 weeks that I will just barely get to work on time for this very reason.
Where I live we have signs that say "slower traffic keep right" and "the left lane is for passing" but I've never actually heard of anyone getting a ticket for it so I assume if it is a law its not enforced, though it might just be that most places here either have a high social trust where everyone does it anyways or if they dont they instead have traffic so dense you will never get near the speed limit anyways.