A lot of it is practical. People tend to live differently than a generation ago. How many people today really want a formal dining room that's separated from the kitchen? Or a dedicated formal living room?
A number of years back I had to have some major construction for structural reasons and it ended up opening up much of my ground floor considerable--and it's really so much better.
I'm not saying it all has to be one big fully open floor plan but generally speaking at least kitchen/dining area and maybe other common spaces are more useful as an open plan.
Hmm… I have no need for having both separated formal dining rooms and living rooms, too, but I also don't want the kitchen's smells, fumes and heat entering uncontrolledly into my living room, either.
A number of years back I had to have some major construction for structural reasons and it ended up opening up much of my ground floor considerable--and it's really so much better.
I'm not saying it all has to be one big fully open floor plan but generally speaking at least kitchen/dining area and maybe other common spaces are more useful as an open plan.