That's because there's no reason for most people to buy another TV. The majority of people who would want one already have a TV, and there has been no technological advancement in the last decade or two that would entice anyone to throw away their already perfectly acceptable large LCD/OLED/whatever television just to buy another one just like it.
The only thing anyone has been able to come up with is making all TV's internet connected and "smart," which is a feature that approximately nobody except the MBA's in charge of the companies cranking them out seems to actually want.