Listen Noobs, there is something called floating geometry or floaters, often used in games with lowpoly, or as part of repeatable asset sets.
Then there are cases where you do speedmodelling or fast concepting, where you generally shit on topo and polycount, you just want to create the right forms( fast). Like Masterxeons video.
Then there are cases where you work for 12 ours to model and texture a background-vehicle for the latest Sci Fi show, and then in the final shot the vehicle is barely visible for 2 and a half seconds. 20 pixel big.
Behind mighty Depth of field and motion blur.
Nobody cares if it isn't (visible) in the final shot.
Also nobody cares if its just a bunch of intersecting cylinders and boxes.
But feel free to connect every piece of geometry you find needs connecting.
Just don't be pissed when people laugh about your autism.