Pro: You get a free inventory system
Pro: You show up on local search results
Will some (maybe most) people go to Walmart instead? Sure, but those are people already using the app, which means that if you're not listed at all, you have absolutely zero chance of winning the business. Unless I'm missing something, this seems like a no-brainer for vendors.
Another way to look at this is: what if the business could use the inventory system for free, but opt out of showing up in the local listings. Are you saying that you think there's a vendor on this planet that would actually choose not to show up in the search results?