I'd honestly describe using the built-in keyboard (and especially trackpad) on most laptops as cumbersome and uncomfortable.
Unless you really need to have a mobile workstation - running between meetings, conference rooms, into lots of labs/industrial environments where you can't bring a laptop cart with monitor/keyboard...why would you not dock the machine?
Even if you prefer the feel of the keyboard or trackpad, wouldn't you want the ergonomics to be better than a laptop if you're working on it all day? A pair or trio of 20+ inch displays mounted just below eye height at about reach distance, ergonomic keyboard with elbows at about 90 degrees, and full size mouse will always be a better workstation than the nicest laptop keyboard, trackpad, and 15" display hinged to said keyboard.