Why do some businesses advertise free Wi-Fi ?

I understand restaurants,fast food places,coffee shops,book stores etc.etc,,,places where a person could sit down,hang out for a few minutes and boot up their PC to surf the net .
but why Office Depot, Home Depot ,Grocery stores and the like,even bother to offer it ? Wouldn’t it be a waste of money to set up free Wi-Fi access to the public as its not as people are going to come in and walk around the store with their PC on the shopping cart surfing the net or checking emails ?

Recently,I’ve seen a Lumber Yard advertise how they have free Wi-Fi . As if people are going to come in just because of it and while there,decide to buy some 2×4s