First off, it needs to be said that monitors have distinct advantages over TVs. Since you sit close to them, you get more “bang for pixel” so to speak. Even an 8K TV looks like regular HD from common living room viewing distances, but a PC gaming monitor? By and large everyone sits just a few feet away from those, meaning every pixel counts – and is accounted for. Further, monitors come in much more affordable prices. If you don’t need a massive screen, then monitors simply deliver better value for money. By the same token, monitors don’t take up a lot of space, so depending on your circumstances, that could be a major consideration.
Finally, gaming monitors in many cases act as pioneers of new technology later picked up by televisions. For a fraction of the cost of a good 4K TV you get a monitor with 144Hz refresh (TVs just recently arrived at 120Hz), FreeSync, HDR, and powerful audio. Monitors also don’t have all the complicated electronics and post processing of TVs, meaning very low latency. Your typical gaming monitor has 1ms response (grey to grey and/or moving picture response time, GtG or MPRT), while very few TVs come even close to that. Most TVs are happy to deliver 8ms with game mode engaged. Monitors don’t need game mode.