Last time I tried a usb switch it would flip out and cause issues (it was doing the monitors too, and it was cheap). I forget what the specific use case was, but at my house we definitely had 2 keyboards on top of each other. It was a temporary set up of two computers at the same station, so didn't warrant looking into a better switch. If I ran that setup daily in the long run, I probably would have.

Someone who's IT department has plenty of keyboards but no USB switches on hand at the particular minute they are given hardware.