Why is a recursive DNS query important?
You would normally use a recursive DNS query to determine the network provider of an IP address. This may be for statistical reasons or for technical reasons.
For instance, you may want to log the website visitors and determine through which access provider the visitors are connected to the website.
You may also want to secure a network or an admin environment by whitelisting IP addresses that ar allowed to have access to the system. You can even record the IP addresses of unwarranted login attempts and determine through a reverse DNS query through which access provider the unauthorized login attempt took place.