I have a Dodge American Clipper 21ft C. A friend has a Toyota Chinook (smaller than the old dolphins with a pop up top). She just got a Toyota Sunrader (newer but similar in size to the dolphin).
I love the size of the clipper and sunrader. They can easily be driven around town as a second vehicle. They fit in a driveway. They fit in most all campsites. They are comfortable for a couple or small family.
The main thing I sed as to why folks go bigger is: 1) if it rains, you want room indoors; and 2) everyone requires their own space.
To me, those desires are driven by public perception and not actual need. For years, kids shared rooms and families lived in small homes without issue. Then, suddenly, if each kid didn't have their own room and bathroom, it was a disaster. Truth is, if you bring up the kids sharing space, then they will be fine sharing a space. And if they do get in a tiff, you do what parents have done forever "go outside and play".
And when did we have to start hiding from the rain. Grab a raincoat, umbrella, and/or garbage bag and go for a hike. A forest rain is refreshing and delightful.