There’s no down-side to selling a smart TV to someone who doesn’t want one/doesn’t use the features.
The features we “want” from modern TV’s like DolbyVision and all the shit they do the image to make it stand out in the store requires a significant amount of processing power.
It’s simply better business to sell smart TV’s to everyone than to make dumb TV’s that compete for a tiny fraction of the market when people buy Smart TV’s in every price segment.