Chicken and egg
ISPs (at least here in the US) are not giving out IPv6 addresses, because
Certain applications-masquerading-as-OSs cannot correctly handle IPv6, because
The company that makes them cannot be bothered to release a fix, because
people don't care about IPv6, because
Websites don't support IPv6, because
People aren't using IPv6, because
ISPs aren't handing out IPv6 addresses, because....
I'm really surprise the cell industry isn't really pushing IPv6, especially for teathering - making teathered devices use IPv6 would reduce the amount of addresses they need and would reduce the levels of NAT they have to use.