It's not just morrisons, all supermarkets have the same issues, specially home shopping departments, when drivers return from their delivery routes, usually 10 minutes before the end of their shifts, they are required to unload the empty boxes, and put any returns back on the shop shelf. The problem is it takes time to unload the van, and by the time that is done they are working past their contracted hours (which is often unpaid without prior approval) so any returns just end up in a pile at back of the depot until they eventually get returned to the shop floor by the picking staff.
The last time the returns got left to pile up there were roughly 60 boxes and 3 trolleys full of stock, some of which were perishables like bread. Most of the larger stores waste on average 10-15k in stock per month, even more over busy periods like Christmas. If you worked in a supermarket as a picker/delivery driver.
You'd soon go back to doing your own shopping.