Not everybody leaves their home every day - or drives past the same pickup-place every time they leave their home. Reasons are numberable and not really point of the discussion.
Basically, yes, there could be some positive ecological effect from requiring customers to pick up their purchases. On the other hand, additional traffic may be created by customers having to drive longer ways or by creating extra journeys from people who wouldn't have left their homes otherwise.
A reasonable choice would be the last mile delivery by only one vehicle/service. Packages from all carriers would be collected at a local location and then distributed by one vehicle per area. Maybe delivery areas would get smaller, maybe you'd have to wait for your package a day longer.
The best choice - at least in urban areas - would be the use of large cargo bikes operating from depots within the city quarters. This is already tested in several European cities.