I'm just relating my experience - when I was younger, I commuted 20 miles round trip every day, and I worked at a bike shop with weenies that were always trying to shave weight off their bikes, so I did whatever I could to add functional weight (so no filling the tubes with lead, that would be cheating) including building up a dually, two rims side by side on a Sachs 3x7 hub. My average speed was higher when commuting (lots of rolling hills, but overall uphill in the morning, downhill going home) than it was on days off, when I was mainly riding around town where it was flat.
And it certainly wasn't because I wanted to go to work...