Hiring an actual IT person to set it up would be a very difficult expense for many small businesses. Cafes usually operate on very tight margins. I just find this law completely ridiculous and an obvious result of hysteria. It is not a rational response to the very tiny risk of the dastardly and scary terrorists using free wifi.
As all businesses require it the chances that ISPs don't offer a service that includes that feature seems extraordinarily low. Seems like knowingly selling a service that wasn't capable of logging, under a legislative background that requires it, would also likely be unlawful.