[pelorat]

IPv6 also makes it unfeasible to scan the whole address space, unlike IPv4 which is regularly scanned.

[otabdeveloper4]

ASN addresses are public information.

[Dagger2]

An ASN with a /32 allocation (the smallest for ISPs) is four billion /64s. It takes dozens of yottabytes of traffic to exhaustively scan one single /64. The entire v4 space takes 0.00000001 yottabytes, or about 110 GB/port in more understandable units.

There's a ton of things you can do to cut down on the scan space for v6, but it's still far huger than v4 can be.