The due date is the deadline. A cot ordered for a birth in six weeks is not a normal retail order, and a supplier delay that would be a minor inconvenience elsewhere is a serious problem here.
Fittings occupy staff. A car seat fitting is twenty minutes with a trained person in a car park, and treating it as a walk-in either rushes the safety check or empties the shop floor.
Gift lists are shared and bought in pieces. Several relatives buying from one list at different times need it to stay accurate, because two identical items arriving is exactly the failure the list existed to prevent.
Large items need storing. Parents frequently buy early and want delivery closer to the birth, which means holding stock for weeks with a date attached to it.