well, the Docsis 3.0 CMTS hardware is quite expensive, if not saying dramatically expensive.
Then, the Docsis provisioning software is also quite expensive, and I haven't heard of any free ipv6 upgrade from any of the software vendors...
then come the modems... well, probably some of them require only the firmware upgrade...
in DSL market, it's even worse: the Broadband Forum has not released yet any ipv6 related document...
apart from that, yes, the engineers are usually lazy :-)
From: "roger@mgz.ch" roger@mgz.ch maybe not all hardware (CPE) is able to handle docsis3 ?
So you were too lazy to upgrade to DOCSIS 3.0 ;-)