Good way to get repeated customers.
Once you have to pay for a membership, you are more likely to buy more and more cuz if you don't, you are going to be paying for something you don't put it to good use.
I don't have a membership but I piggy back with my cousin. He buys all the time and delivery comes to his house on the daily. I'm like WTF? Is he running a warehouse operation or something? Nope, all them boxes are for him. I only piggy back with him for the fast free delivery.