If you really want to know the truth of it, it's because the industry gave up on pushing for high adoption rates.
Main reason for this was 1080p or less was dirt cheap, and people weren't willing to pay enough more to generate big profits.
They did much better with the "smart TV," for dumb people who can't figure out how to hook up their own computer to a TV. Not sure but I expect they get a cut from the providers like Netflix whose apps come preinstalled on the TV. If you can't watch whatever you want for free nowadays, you're computer illiterate.