Time Warner Cable certainly doesn't, but I was surprised to find that even Verizon doesn't provide it for many (most?) of their FiOS customers.
When pressed about IPv6 support, ISPs, typically respond that very few services require it, so it's not a priority for them. But this is a catch-22 - the only reason so few services require it is that so few people have access to it!
And the people who suffer the most aren't their customers - it's people in other countries who are forced to live behind NAT because of IP address exhaustion.
For example, the entire country of Qatar shares a single IP address: http://en.wikipedia.org/wiki/User:82.148.97.69/header