The more pixels you throw at font rendering, the better. It also allows for cleaner upscaling from lower resolutions. However, those two uses are needed more on

The more pixels you throw at font rendering, the better. It also allows for cleaner upscaling from lower resolutions. However, those two uses are needed more on computer monitors, not TVs. You are right that most folks with 50-65" TVs at 2-3 meters don't benefit from anything higher than 1080p.