Pretty much why a tv is still a poor choice as a monitor. Also why choosing a tv with less than 1080p regardless of size is a bad idea. Even though a smaller tv may not benefit visually from 1080 resolution it adds a limitation technically that you could avoid simply by buying 1080 to start. I bought a pair of 1080 monitors this time around specifically because of that and a because of a couple other more specific reasons that mainly revolve around what I do.
My question though is why choose a tv vs a display designed for pc?