Simple, safety and traffic. Motorcyclist are statically safer to lane split or filter in higher density low speed traffic than to abide by the same rules as cars. Traffic being a added bonus to the safety aspect, often times cutting commuting times in almost half for most riders vs car drivers. Take that into account an congestion could be reduced for EVERYONE by almost 60%. When considering what you have read just look at how many cars on your way home have only one person within. Thank you.