As long as everything else about him is the same, I wouldn't worry about it at all. I would imagine it is more a temperature thing than it is a hide/no hide thing. If you set things up where you have both a hide over the heat and another on the cold side then you will probably see him use the hides a bit more. But with my experience with carpets, a good portion of them don't care too much about hides and usually only use them when they are going into shed.