I think this is more niche to care about than you might imagine. First off, a huge % of the population barely knows what an HDMI cable is and just doesn't plug their laptop into anything. Second, office workers might have a nice docking station setup, but in that case you are probably basically turning the laptop into a desktop (with a keyboard, mouse, and nice monitor) -- why bother with the laptop screen at all? Finally, perfect DPI matching isn't really required -- a 1080p laptop with a 1440p monitor should probably be fairly reasonable looking for most normal screen sizes.