An adapter exists to drive an external display and power. The reality is, a secondary display for most (read: casual, mainly nontechnical consumers who certainl

An adapter exists to drive an external display and power. The reality is, a secondary display for most (read: casual, mainly nontechnical consumers who certainly don't read Hacker News nor know of its existence) people is not a priority. Sort of like how inserting a DVD into a computer is no longer a priority for me. It cannot support 4k @ 60hz. I know this because I also own a Dell 27" 4k display to pair with my main machine. I have only connected the Macbook to the display via HDMI (by means of said adapter). It supports 30hz at best. I have not tried a 1440p display. It (of course) runs at 1080p just fine.