As a network security engineer, it allows me to look at my public-facing IP addresses, and it also gives me an at-a-glance overview for IP address ranges that seem to be attacking me, without the need to fire up nmap, nessus and nikto for a "retaliatory" or "recon" scan.

Just like Johnny Long's GHDB, a list of search operators for Google that reveal sensitive and/or vulnerable services or data, there are both creative/beneficial and malevolent uses for these tools.

Also, "research" is a completely valid reason.