I think their big thing is speed. They are scanning the entire IPV4 space in 60 minutes which... is kind of impressive? I haven't thought about it but doing a port scan on my public network takes a little bit of time and I'm only dealing with couple dozen IPs.
You only need 1 Gbit/s upstream and a laptop to hit the 45 minute mark. On fancy hardware zmap needs less than 5 minutes.
One of the people behind the project presented it a 30C3 a few years back (including a live scan) in case anyone is interested: https://media.ccc.de/v/30C3_-_5533_-_en_-_saal_2_-_201312281...
I'm just browsing their website some more, they seem to have lots of interesting libraries too, like https://github.com/zmap/ztag
"ZTag processes ZGrab output and annotates raw scan data with additional metadata such as device model and vulnerabilities."
Surely the technology will be cheap enough to do at some point.
(To reach to the capability of what google is doing right now, not to surpass what they will be doing then )