I'm one of those players who quickly gets sucked into buy a house in any MMORPG that offers the option, and then usually ends up buying Premium decor to decorate the place. I hate to think what I spent (in real money terms) on decorating my string of houses in Black Desert Online.
Having a customisable house in BG3 would be a fun option. As others have said, if nothing else it would be a good place to display all that interesting junk you pick up. Leaving it around the camp just looks untidy to my eyes.
I feel you. I have all available houses in Star Wars - The Old Republic, all rooms unlocked and am constantly redecorating.
I love houses in games and put far too much time in them, when they are available.