"How many people are doing that?" Probably very few. AFAIK, wired keyboards were never officially supported. Plus one needed the "Camera Connection Kit" adapte

"How many people are doing that?" Probably very few. AFAIK, wired keyboards were never officially supported. Plus one needed the "Camera Connection Kit" adapter (later rebranded as Lighting to USB connector). Plus some USB keyboards would not work. The only officially supported keyboard option was bluetooth keyboards. In the real world, I have never seen anyone plug a keyboard into an iPad. I have only seen people use bluetoth keyboards.