I suspect that part of the problem are the changes in our emissions and noise regulations over the past 30 years. Honda's CB1100 from 30 years ago produced much more power than the new bike, but of course, it did not have to conform to 2014 regulations.
I wish that our EPA was required to do a cost/benefit analysis before imposing new rules. IMO, the relatively few (compared to cars, trucks, and even lawnmowers) motorcycles ridden in the U.S. cannot make a meaningful contribution to air quality numbers.
Bob