iPads, and even iPhones, can connect to Bluetooth keyboards and use them just fine. In fact, some UX exists solely if you have a keyboard, such as the Cmd-Tab task switcher. The iPad Pro models also have the smart connector keyboards. They're pretty decent - as a touch typist I have no problem using them.
That said, an onscreen keyboard is fantastic when you just want to hold the device in your hands. Would I want to do a ton of typing that way? Absolutely not. But when it's useful, it's incredibly useful.