The round is the economics. Which clients on which day, in what order and how full each is likely to be decides whether a van is profitable, and driving in the order the calls came in is not a route.
Containers live at customers' premises. Which ones, what size, since when and whether they came back at the end of a contract is an asset register that most small operators simply do not keep.
The document is part of the collection. Generated on site, with quantity, date and signature, it is what the client keeps for an inspection, and producing it later from memory is not the same thing.
Volume history sets the schedule. A client collected fortnightly who is always overflowing needs a weekly visit, and one who is half empty is costing a stop that could serve somebody else.