It’s not always cheaper to buy online. The brick and mortars pay their shipping by the truck and save that way. Online retailers have to charge shipping by the item, which can add up.
Buy online from Walmart and pick up at the store
Buy with Amazon Prime
Buy with E bay free shipping
Not if you can find free shipping - or even low, flat rate shipping.
Its just more convenient to have bulky items shipped to your door.
One doesn’t have get in the car and drive to the local store to pick them up.
Since, I’m car-free, certain things I have to buy online as its impossible for me to transport them home myself.
Retailers don’t carry everything in their store that they do online. I’d rather order it than to make a trip for nothing to the store.
It also often depends on what part of the country you are in. Brick and mortar is more expensive in more expensive areas. What the online sellers are doing in part is recovering some of the savings that people in high-cost areas can get by shopping online.