Yup, shops themselves had massive stores of stock. My father was manager of two Redmans stores (part of a national chain up to the 70s). Both had cellars, same size as the shop floor, one had one upper floor, the other had two upper floors. All levels always full of stock. In the cellars were large freezer/fridge rooms where they stored the perishables, i.e. cheese, butter, meat, etc. That was because it could be weeks between deliveries of non perishables like tins/packets/soft drinks/tobacco/alcohol, etc, so they needed to keep several weeks of stock. Even the perishables didn't come daily, more often every week or two.
He left and bought his own "corner newsagent" shop where we lived in the flat above - we literally lived among the stock - it was piled in the hallway, bedrooms, living room, kitchen, garage, and a couple of sheds in the garden. Seasonal stuff for Xmas, Easter, etc was stored in the loft. One year we even had a massive surplus of fireworks which we stored for the following year! In the first Easter, the previous owner had grossly over-ordered easter eggs (we suspect deliberately), so we could barely move for the damn things all over the living areas.
Nowadays, "just in time" has meant none of that is necessary. Even big supermarkets have relatively tiny storage areas - more for just handling deliveries than longer term storage. As we saw with the Co Op delivery chain outage last year, the stores didn't last more than a few days before the shelves started to become empty.
We've gone from shops having 2 or 3 times the shop floor space for storage to the opposite where the shop floor is 2 or 3 times the storage space.