I'm in Ralph's camp, stayed in medium format basically because of the practicality and lifestyle. I want to be mobile and even mostly handhold my medium format (I know!).
If I were to move up to LF, I would love to do 8x10".
medium format have now been completely replaced by digital imaging
For me "finally" around 2022-23 ditched 35mm but the larger medium formats still keep that particular look so I am happy with my GW690. Aside of resolution and pure image quality aspects, there are the classic film characteristics which might be preferred. I'd say more than pure resolution, larger formats have that drawing due to the FoV and longer focal lengths.
As of phones, am more than happy that they are good and better for snapshot photography. Still have very good quality and nowadays with large-ish sensors too. Interestingly, sometimes the fixed large aperture of its lens and on some near subject there is a larger than expected format look (bokeh).
With modern films, Tmax 100 200LPM, very small grain, in 8X10 to 16X20 a 6X9 negative provides enough detail and small grain, sure a 4X5 will have more, but detail that you really cannot see at viewing distance.
An economic reason is the price per frame. Locally there are a few LF photographers, but running T-grain type films in smaller formats does punch very nicely up, whereas I see most of them sticking with Fomapan due its affordability. Then color, is a whole pricy (but beautiful) ordeal.
I rarely use the 4x5 outfit I have as I am more than happy with the size of prints I am making from medium format (Pentax 67), currently 60x49cm for exhibition, though I can go larger if cost is no object (and it is!). Similar case using 35mm and top-drawer L-series Canon lenses. Besides which, I do not have the patience of a Hindu cow now for the dedication and fiddling requisite of LF.
You win the comment section. I share the feeling about not having the patience of a hindu cow!
I have however helped out studio setup 4x5 and somehow been rather proficient at using it despite never owning one.