Your trade area is bigger than your parking lot
Plenty of customers in your area cannot or will not drive to a dispensary. Delivery makes them reachable without a second location.
A cheaper form of expansion
Compared with opening another store, a delivery territory is a small commitment with a fast read on demand.
Keep the store at the center
The point is not to move your business into an app. It is to let your existing store serve more of the people around it.