I used to live about 3 miles from school, mostly very flat. It was nice to be able to coast through the flat part. The school was on a small hill. So to get home at night, I could roll down the hill picking up some speed, then coast the rest of the way. A dynamo would have used up that energy.
Dynamo lights do add resistance, but unless you’re racing, it doesn’t really make too much difference. The bigger hurdle is the high cost of the hub
I used to live about 3 miles from school, mostly very flat. It was nice to be able to coast through the flat part. The school was on a small hill. So to get home at night, I could roll down the hill picking up some speed, then coast the rest of the way. A dynamo would have used up that energy.