The same is true in the Netherlands. Honestly, if they are biking around campus, they don’t need helmets. Helmets are needed on American roads because of poor biking infrastructure (not an issue on campus or in the Netherlands). The article is taking liberties using nationwide statistics to criticize local behavior.
Are you sure? Just falling over on the bike while stationary (I admit I've managed this before) without being able to partially break your fall. could outright kill you if your head hits the pavement. (An uncontrolled fall from standing height to concrete such as by fainting can kill.) Even if you don't die, head impacts are really bad for the brain.
I've only been to Amsterdam a couple times but my favorite snapshot of biking there was a lady biking hands free fiddling with her eye makeup (I think?), being passed by a hands-free dude wearing a suit, talking on his phone with one hand and other hand just kinda hanging alongside his body ;)