If we're looking at the portion of traffic, most of the big bandwidth heavy services (the video streaming sites and CDNs) are on IPv6, the long tail of IPv4-only services tend to be lower bandwidth stuff.

I believe one big anti-incentive is rate limiting, especially nowadays. With IPv4 getting a range ban is somewhat effective, way less effective on ipv6 (theres a reason HE tunnelbroker is marked bad nowadays, discord bots doing music load balance over ips on tunnelbroker for pulling youtube audio data.. they ban a /64 but you balance over a /48 or bigger). I believe this was the main reason Discord disabled IPv6 (not sure if thats still the case, but it was back in the day since bans and api rate limiting was ip based).

Why is it less effective on v6? You just ban the /48 or bigger.

It's difficult for servers to know how big client allocations are. With v4, pretty much everybody got /32s, but with v6, sizes vary. So you've got to start with small bans, and then switch to big bans later, but not too aggressively so you don't accidentally ban legitimate customers. It's a tricky balance.

You have to do that with range bans in v4 too, since you have no idea how big the pool of addresses a user can pull from is -- and with CGNAT in the picture you're kind of doomed to banning legitimate customers on v4 no matter what you do.

Yes, you ban some legitimate customers with v4. But the span between the smallest allocations and biggest allocations is much smaller, so simple strategies (like banning the bad address) scale further.

I think the span would be about the same, or smaller even, if you limited yourself to a granularity of 4 bits for v6. Allocations are often rounded to 4 bits in v6 because it correlates to exactly one character of the v6 address.

I'd also like to note that being worried about accidental overbanning in v6 but then being dismissive of it in v4 is a double standard.