Because if you own a TV manufacturing company, you can sell more TVs if they have more features. You can get more features by including a linux SBC and integrating it. In fact, some of the paid-app makers will even _pay you_ for this "real estate". You could make a dumb-tv, but you wouldn't sell as many and you would have to charge more.

> and you would have to charge more

Non-commodity consumer products are rarely sold at cost but rather at whatever price the market will bear.