now for an explanation
it's basically due to many LCD sets' low DPI (dots per inch) rate, that's obviously more visible when the LCD panels' picture is projected on a big screen
so the higher the panel's DPI rate is, and the higher its resolution is, that problem gradually disappears over time as technology improves... if you recall early computer LCD monitors from just a few years ago, they were small and their DPI rate was very low, so its pixels contours was very visible, it's not really a problme with recent monitors now... that's why I don't like small low-rez LCD tvs, it's just too visible
also, certain conditions and video sources will show this make this default more visible
with 1080p panels the DPI and resolution is so high that it should completely stop being a bother in any way