I'm guessing the first order (a whole house!) was more than large enough to cover the cost of an extra free delivery though. This is about relationship management at that point, which won't be the same for a hobbyist only doing one smaller project.
The point is hobbyiests don't visit often enough to be worth figuring out how to charge for shipping.
Note, at a real lumber yard you need an account. They can accept cash sales but they would rather not. They won't talk to you if someone else with an account is there. Once you have an account (which is free) you have passed the initiation and they love to help.
