Because such thing does not exist, it's called PI and is not available
to IPv6 end-sites. And if it ever is, it will cost money or other
annoyances to obtain.
SLs won't come for free either. Architecture aside, I prefer people
that use a service to pay for it rather than the community as such.
Then I also happen to think that SLs break the architecture but that is
something else...
- kurtis -