Well, the cars are getting heavier so they need more power to move them. So it is not just a progression of adding power - they need to power to get the same performance. So the actual performance hasn't increased quite as much as the horsepower would lead you to believe.
Just look at how big a regular Accord has become. Yeah, it now has 250+hp but it needs it to move the 1000+ lbs increase in weight.
