You could write whole books (and people have) on the history of the shower. But the history of the shower head itself is very brief.
It's not because shower heads are new. Modern shower heads have been around for nearly 250 years. It's because there hasn't been much development over their history. You might be surprised to learn that most of the shower heads being sold today are not significantly different in design from the ones our great-great-grandparents used. ..
High Efficiency Showerheads
David Malcolm, Monday, February 15, 2016