We all have "Turn On's". People who over indulge in porn experience a diminishing sense of their turn on's as they have explored and had access to so many of them quickly and in succession. At a rate that would be impossible to experience in real life.

I am sure that many porn watchers switch categories because the former simply does not do it for them anymore. That impacts real life scenario's and as a result you may not find a naked body stimulating unless X, Y, Z.

We also have muscle memory, and the longer you train yourself to respond to stimuli generated by porn, the less you give yourself the opportunity to be stimulated by real life scenario's. Your body will learn to respond to porn only.

The talk I posted is much more articulate than I was and I highly recommend it.