why are we no longer able to DVR record channels on free preview Cinemax/HBO

Why has Cox disabled the record function on the free preview channels? You used to be able to DVR record anything on those regular channels during the free preview to watch when you can, now it says record function not available and must subscribe to record. That is what a DVR is for, to be able to watch things that you are unable to watch "live".  When was the record function disabled and why?  It greatly reduces the appeal to have a free preview.