There were some comments earlier about how Europeans don't worry about cycling gear. Here would be a few answers why:
1. Their bikes are setup for commuting. Granted a nice bike in Holland (when I was there 2 years ago) goes for a low end of $500 all the way up to $1500. These are wonderful year around bikes, what work very well in the Dutch (or Danish) climate. They are heavy, but durable, keep the rain off you (fully enclosed chains, skirts protector in the back), a rack strong enough to carry a passenger (illegal, but everyone does it), amd importantly lights for riding after dark.
2. The temperatures in those countries are VERY mild. When I was there end of June/early July back on '08 the highest temp was 78F and most days it was 68-72F. When I got home to "the Frozen North" that is Buffalo NY the average day time temp at that same time was 85F, that is a big difference. I can ride my biek causually at 68F and not sweat much, if I ride at 85F, I sweat like a pig no matter how relaxed my cycing is.
3. Most Dutch and Danish city dwellers my ride they bikes almost daily, but most don't ride more than about 1 to 2 miles at most. My cousin who now lives in the Leiden area has always ridden his bike a lot more than average as he commuted 5 miles. Most Dutch consider that a very LONG commute. In all honestly I never met anyone in Holland that commuted much more than 10 miles on a bike. When I was little my father commuted from Haarlem (Schalkwijk) to Fokker (Aircraft factory) and that was about 8 miles. That was considered pretty extreme. When the weather was bad he could take a company bus that came out our way.
I agree with all the comments that cycling in and of itself is easy, but a 13 mile commute does take a bit more prep then a simple 2 to 5 mile commute.
I've ridden 15 miles back and forther between office on an unexpectedy warm day using my tights and cotten underwear... big mistake, I rubbed the skin off parts of my inner tighs. I feld realy silly getting out the diaper creme. Cycling shorts have their place. I don't bother with rides under 10 miles, but with longer rides, "regular" clothes can cause some bad chafing.
Happy riding,
André