My husband, a German, has been putting his fingers on the scanners when coming in to visit my family for nearly two decades - turnabout is fair play, I suppose...
That's the idea with a lot of immigration policy. Strange this one wasn't already reciprocal. Whoever originally designed it felt that Europe needed American visitors more than vice versa, but now, that's not the case.
I don't think "back at ya" is the goal here. There are many practical and good reasons to have fingerprints of people entering/trying to enter your country. Most are the same reasons that you have to give fingerprints in domestic situations.