I can see where you are coming from. If I carried a photo gear specific bag or shot in a studio I would have little use for a smaller camera.
For my purposes, it's great. I carry a briefcase / edc bag everywhere and go into the city a lot with a single bag. I want to ALWAYS have a camera with me, and for awhile this was a little Panasonic GM1 or a Fuji X-E3. Having the option to have ONE camera that can do it all and pack small and light is fantastic.
A thin and light FF mirrorless camera with a compact "all around" prime (pancake please) is ideal for my every day use, and I can slap on a zoom or a tilt shift for the days that require it. I now often carry a 6D with a 40mm pancake which I like...going even smaller and lighter, and with some additional resolution, video features and DR would be even better.
But for days where I am already going to have to carry a lot of gear and a tripod, or where I am in a studio like environment, a larger camera would actually be slightly preferable, as you mentioned. Options are good.