It's a fucking glockenspiel

Is very simple really: xylophones have wooden notes, glockenspiels have metal notes. So why do people keep calling glockenspiels xylophones?

Glockenspiel

But I want to bang on a bit more first, with some etymology. Xylophone comes from the greek words "xylon" meaning wood, and "phone" meaning voice or sound. (We are all faimiliar with telephone meaning "far away voice".) Glockenspeil obviously sounds a bit german. Glocke means "bell" and "speil" means speech or some shit (the literal translation is "play"). And lets face it the sound of a glockenspeil is not so dissimilar to that of a bell. So, xylo-phone = wooden-voice, glocken-spiel = bell-voice.

Xylophone

I can only think of one possible reason why people would get this wrong so often, and that is that there aren't many words that start with X. You want to make some sort of picture dictionary for children who are just being introduced to letters and the alphabet and you need something to go on the "X" page. Naturally you stick a xylophone on there. So when your child gets their first toy glockenspiel a few months later they (and you) have seen the word xylophone recently, but not the work glockenspiel.

Argh, the rage...

Here are some entertaining videos of people playing glockenspiels.

Here is an entertaining video of one of the most famous xylophonists of the modern era.