If it’s heavier, you need more power for the same performance.

I‘m not sure I agree you on “nobody asked for more power”. A lot of people don’t want a sluggish car when they are trying to merge. People “ask” via their buying patterns. They’ll look to a V6 if the 4 banger is too puny. They‘ll look to a competitor.

I got the v6 accord for power, speed, and reliability. Almost 300hp with a manual is a lot of fun for a daily commuter.

You don't want that lighter weight body, though, you just think you do. With the lighter weight body you lose a lot of safety features. You have fewer airbags, fewer crumple zones, fewer sensors giving you information about your car and road conditions. Modern vehicles sacrifice that slight bit of efficiency for a much, much safer driving experience.

>nobody is getting accords for power/speed

True, but speed isn't the only reason to have more power. There is safety measure, but also luxuries. I like my divertissement screen, the GPS, the collision detection, the heating seat, etc. All of this mean more not only more weight to carry around, but also more electricity that come from the engine.

I also like to have a responsive car and a smooth acceleration, and for that you need more power. You don't really need to put the engine to the max to reach illegal speed on the road, but a more powerful engine change drastically how driving the car at low speed feel.

>I want that more efficient engine in lighter weight body to maximize efficiency

And there is other models that do just that. That said, those models are a lot less popular in North American compared to Europe so there isn't as much model available. Manufacturers sell what the market want.