Here in Europe, at least in 2013, the adapter had two ways of plugging into an outlet: a cable and a plug that could be clipped on. The plug only had two prongs, while the cable had a ground connector. I'd get the "buzz" if the adapter wasn't grounded.
This also happens with my HP laptop if I plug it into an ungrounded usb-c adapter, so I'd expect the same thing to happen to iPads.
We have many Windows laptops in the family, and everyone uses mice most of the time. I only use a mouse on my Macbook when it's hooked up to an external display. Even then, I sometimes wish I had a Magic Trackpad.
Yup, at work we have "high end" enterprise HP Elitebooks. We've had a general refresh 1.5-2 years ago. Basically, everyone lugs around a mouse. And they're not "nice" mice, either, so it's not like they're getting any extra fancy ergonomics or what not. Hell, generally they're the basic 3 button Logitech, without even a back button (don't know how people can go without this today).