Hi Alex
the biggest (though not the only) reason to create SKUs for location is the ability for the branch/warehouse to define their own replenishment and planning parameters for the item. Some branches/warehouses/locations don't need replenishment and stock planning at all (for example, returns location, or some 3rd party distribution points) so there is little point in creating SKUs for these. However, if the location requires to run replenishment (MRP, MPS) then it would only make sense to create SKU for it. Otherwise, as you rightly said, having some locations using replenishment/planning parameters on SKUs and some on Item card would confuse users.
Hope that helps.