Wasted space in houses? Or some kind of usefulness?

I’m getting tired of living in this tiny shoe box apartment and I’m thinking that next year I might be in a position to buy a house.

When I was with the wife we rented a couple of homes in the Austin, TX, area and I noticed they had a “feature” in common that I couldn’t wrap my head around. This was space that couldn’t be used.

For example, one house had a dining room that was a fair size. Not huge, not tiny. It was on the first floor and it didn’t have a ceiling. There was empty space all the way up to the second floor ceiling.

I always though that if they put a floor up on the second floor you could get a larger family room, or make slightly bigger bedrooms or (if you had four kids) another bathroom.

I could only think of two reasons for having it this way: aesthetics and, maybe, during the summer months all the hot air would pool up into that empty space (in practice, this didn’t seem to happen).

Is there another reason why nearly every home down here since 2000 has been built this way? With huge empty space? Or is it really down to the look of the thing?

I will mention two other downsides to this kind of floor plan: during the winter doesn’t all the hot air you want to heat the house end up in this empty space (if it worked for the summer, that is)? And, from personal experience, cats can fall from these heights and children sometimes try and brave death by jumping (successfully stopped in my case).