1366x768 was a resolution of monitors. It got translated into TV panels despite 720p being the standard. Most of the early HD TVs were actually 768 as were many monitors at the time. Everyone who was making the high quality TVs aimed for 1080i and then of course a year or two later 1080p was easy and that is where the standard actually finished up. But we still have quite a lot of those old panels for sale, but really they were kind of re purposed PC monitors rather than designed to be HD TVs from the outset.