Bending the edges of the image towards you makes you feel as if you’re seeing a wider image than you get with a flat screen. Draw lines from your head position to the edges of, say, a 65-inch flat TV and then draw lines from your head position past the edges of a 65-inch curved TV to the same plane you’d have been watching the flat screen in, and the curved screen’s image appears to stretch further across the wall than the flat TV image, despite the screen sizes involved being ostensibly the same.
The argument goes that curved TVs track the rounded shape of our eyes better, and thus deliver a more focussed, comfortable image than flat screens. This argument is born out to some extent by the use of curved screens in commercial cinemas, where the curve helps the projected image retain even sharpness right into the corners of their vast screen sizes.
To be fair, the idea that you need to be sat in a very specific ‘sweet spot’ to watch a curved TV hasn’t proved as fraught an issue as we’d once feared, since the 70-degree effective viewing arc provides enough room for multiple people to watch a curved TV without the curve actively upsetting their experience. But at the same time, the area within which you need to sit to fully appreciate the curve’s benefits is in still quite small.