Monitors have other purposes of TVs, the things that are important on a monitor are not the same on a TV, and a good monitor doesn't necessary mean that it's a good TV or vice versa.
See the same difference in the audio world: there is monitor/studio equipment that has the purpose of reproducing the sound as closely as possible to the original media, and then there is listening equipment that is meant to make the sound more enjoyable for the listener.
Monitors also doesn't include a TV receiver. While that can be an advantage in countries like mine for people that wants only to look at internet content since if you have a TV with a receiver you have to pay a tax, it doesn't work for people that just want's to watch TV, meaning connecting the power and aerial cable to the TV and use it. You need an external decoder, that needs to have a separate remote control, you then need two power outlets, more cables, you then have to install the decoder somewhere, it's not as clean as having it integrate in the TV itself.
I think especially at my grandma, that doesn't have internet, and wants a TV that is as simple as possible, press 1 on the remote and the TV turns on at the channel 1. Press volume up/down and the power button. Nowadays it's difficult to find TV with that requisite, modern remotes have a ton of buttons what will bring up functionalities that then are difficult to exit, especially for an 85 years old woman that never used a computer or a smartphone or anything other than a TV and the landline phone.