Big box will never buy me lunch
Nor will they send a truck on a special delivery w/ $20 worth of material so we can finish a project on time.
Nor will they ship multiple orders, packed separately to 3 locations on the same jobsite so we don't have to
Nor will they special order parts and get them to me in a reasonable time
If you are a contractor, find a local supply house (whether national or local) that you like to deal with. Get to know the counter guys. They will make you more money than any added expense you may find.
Pay your supply house bills with amex, then use your points around christmas time to get the counter guys amex gift checks. They will love you.
Supply houses are about relationships, big box is about lowest price. How can you expect to convince your customers to look beyond price to service & quality, if you can't convince yourself?