The greatest thing about an iPad is that it's all screen with no space taken up by controls, which is great for consuming content, but not so much for creating it. An iPad keyboard is the great equaliser. Typing on a touch screen is difficult, and it takes up valuable screen space which negates the biggest advantage of an iPad. An iPad keyboard such as you can find on eBay gives you back that space.
You can find keyboard docks for use at home, or keyboard covers to turn your iPad into a miniature laptop. There's no reason to cover the screen with keys, when you can connect a keyboard and start typing.