The order is the record, not the bill
A customer hands over fourteen items and collects them three days later, so the order — the count, the item types, any marks noted, and the promised date — is what the whole transaction rests on. Recording it properly is what prevents the two arguments this trade actually has: a missing garment, and a date that was remembered differently.
What is still in the shop
At any moment a laundry holds goods belonging to dozens of customers, and knowing which orders are outstanding, whose they are and how overdue they are is the operational question of the day. That list is a report rather than a walk through the racks once orders are recorded, and it is also how uncollected goods get chased before they become clutter.
Hotel, hostel and institutional accounts
A hotel or hostel sends a large quantity regularly and settles monthly, which is a running account rather than a counter transaction. Recording each pickup with its counts and producing one statement at month end is what makes that account verifiable — their housekeeping checks the counts, and a statement they can check is a statement that gets paid.
Service rates by item and treatment
A shirt washed, a shirt dry cleaned and a suit are different rates, and express service is a premium. Keeping each as its own item means the bill is correct without anyone remembering the rate card, and it lets you see which services actually earn — express work, for instance, is often priced out of habit rather than out of what it costs to deliver.