Then there is the cost of cable, which is absurdly expensive. To get all the channels you want, you end up spending a couple of hundred dollars per month.
Want to do the cord cutting route? Well that is trending to be even more expensive as each service charges about 10 dollars per month. That doesn't even account for live sports.
The TVs themselves seem to be going obsolete every two years. First it was HDTV, then 3DTV, then HDTV 4K. On the tech side it was LED, LCD, ULED, now OLED. Remember when your CRT TV lasted 10+ years?
Edit: Also they don't get updates after six months. Apps stop working as people have mentioned. But more importantly, they don't get security updates. So your Smart TV morphs into a Creep TV where hackers have their way with it to do their bidding.
Overall, it is easier to just not do the whole TV thing. You will save a ton of money and be much happier at the same time.