Or: it just "shows" better when they're demo'ing the TV to a potential customer, not unlike the hyper-saturated nature footage they use to get you to look at their TV and not the one next to it.
I don't buy that. Why would motion interpolation look better in the store than it does in your own home?
I think it’s because of the content used for it. Some things do look better. But movies absolutely do not.
Because the store chooses to show footage for which it is optimized, not a movie. But there's also the consideration that it looks better at first sight when you walk past it, than it does when you watch a whole movie looking straight at it.