That would depend on the area you're in - sometimes there really are no shops in a certain area at some point.
Also, there are shops that require shoppers to be a certain age or gender to do them, and won't appear on your Available Shops page otherwise.
If you want to see more shops around you, you can set the search distance filter (in the upper-left corner of the Available Shops page, above the map) to 50 or 100 miles, and click the search button (a small magnifying glass symbol in that same row) - that will show you the available shops in the wider area around you. Please keep in mind that this only works on the browser website version - not the app or mobile site.
You can also open a support ticket for iSecretShop and get reliable info on whether there are any shops in your area or not, at any given time.