>>>>so why not simply manufacture televisions with inbuilt consoles?
For two reasons:
1) What console do your put in the TV, the PS4 or Xbox One, or some other console?.
The minute you put any console in the TV you are limiting the person who buys the TV to that console only.
2) What if you put a console in the TV (say a PS3), then Soy bring out the PS4.
The person with that TV is then either stuck with a TV with an old console, or a console they want to replace.
Far better to make the games independent of the device.
In the way that browsers will run on every device so are independent of the actual underlying hardware and software.
I used to work in IT before the days of the web and browsers and it was so restricting that you had to have a piece of software that exactly fitted the hardware and operating system you ran.
The brilliant thing with browsers and the web its that it did away with all that, now the same web site (within reason) can run on a PC, a Mac, a tablet or a smartphone.
Gaming should go the same way, a standard platform across all devices.
I am sure Sony and Microsoft would like this, save them having to spend millions developing new consoles every few years.