I would probably still get an LG G3 or whatever smartphone with a 2k display but not because the res is at 1440p. But because they are very good devices that happen to have a 2k display that I generally don't look for.
That's why they did it: Plain marketing, some people believe its better and the others don't care, because it's a very interesting and good phone.
The truth is: The LG G3 would be a even better phone with a HD Display. (Battery life , Frames Per Seconds esp. in games, Display brightness, "colder" phone) I don't say the G3 is bad at those things, but that it could be better.
Why would someone want to trade those things for a barely better screen in terms of sharpness?