In the case of a brick-and-mortar retail store, you'll probably find a lot of your online visitors to your website are physical store visitors. My wife owns a pet boutique, and almost all of our ecommerce store traffic are people who visited the store in the past week. Some buy online, most call her after and ask to buy things on the website.
Example:
- Customer comes in and browses the store.
- Customer goes home and thinks about that super cute pink collar that would look great on their poodle
- Customer goes to her website, which is a online store
- Customer most likely comes back to buy it. Sometimes they call and order it. Sometimes they order it online. Either way, we got the customer to stay interested and to come back, either to a physical or a virtual property we own
As global as the website is (everyone in the world can see it), I find in her case that it's mostly people within physical proximity from the store that visit, browse and buy. I can tell you that, sitting there on Saturdays with her while she works, almost every person that comes in says: "I was on your website and I saw this really cute <fill in cute product here>.. do you have one I can see?"
Hope this helps - I believe there's definitely value to having an online store, even if it just ends up being a online catalog for your products.
-mjs