Because you/they can develop individual sheets how they want them for the zone system. Also frame precisely in a way that's difficult or impossible on a hand camera, wait hours or days for the weather, etc. A miniature camera is not the best tool for that approach.
i see what you are saying ...
it is very easy to generalize and suggest that all or most or ... people
who use a LF camera use the same methods you described
and people using smaller cameras aren't as patient or methodical in their approach ..
but there are small format users who have the same relationship with their equipment + materials
and exposure methods as LF camera operators you describe
and there are people who use LF cameras who do not use the zone system, wait hours or days for the weather &C
and they do not process every sheet one at a time ...
the way i see it ( and it might be wrong ) is if the person using the camera has a relationship with his equipment and materials
( like you described ) it doesn't matter what camera or materials he or she uses because he /she is familiar enough
through personal experience, knowledge &c with the materials + equipment they don't need to worry about much.
its like knowing how to read the light and not having to deal with using a light meter ... or not measuring ingredients when
making a developer, or mixed drink or cooking a meal ... experience and comfort trumps all.
if the OP is comfortable with using whatever film he grabs and puts in whatever camera he uses
and developing the exposed film in the developer he has grown fond of in a way he is used to ( and it gives him
images he is able to work with ) i don't really see what is wrong with that ... not being bogged down with the minutia
that a lot of photographers tend to obsess about allows him to do what he wants ..