I’m a huge fan of having my own space on a trip.
One of my best friends and I did the Torres del Paine circle in Patagonia a few years ago; had we shared a tent we would not be speaking to each other anymore.
On my first JMT thru my friend lost his tent and didn’t realize it until we were completely down from the pass (he had the fly creek cinched to the bottom of his pack and it just slid right out…). Â There was quite a bit of discussion about his fitting in the vestibule of my duomid (i only had the solo inner) if necessary – but then some folks we were leap-frogging with caught up with us and handed him his shelter.
So basically I certainly WOULD share a tent if necessary, but shelters are so light these days there’s just no reason to share under “normal,” 3-season regular trail hiking kind of trips.
Besides…that way I can pee in the vestibule if I have to.