Because selling the data your SmartTV collects, is a massive revenue stream for these companies. Selling only dumb TVs wouldn’t be as profitable as a SmartTV would be.
Also the ad space that could be projected to these, based on collected data is another massive revenue stream.
Here in Missouri, home owners insurance is starting to lose hail damage from coverage. Damn near 90% of the houses around my area have now replaced their roofs, and have the roofing signage out front. It’s almost a running joke now: guessing which house will be next to get one, and counting the company’s signs to see who’s making a killing.