I get what you're saying, but even though I also think that's a ridiculous amount of space for two people without kids, plenty of people's purchase decisions are based on factors beyond the functional.

Some people like feeling of living in a palace. We have after all for millennia equated living in huge spaces with class and prosperity, and The industrial age, especially in last 30 years, has enabled more people than ever to live in palaces.

Of course, heating a six bedroom palace in Minnesota is no joke.