PIED theory

it seems that its a matter of two kinds of contitioning.

1) visual stimuli in the absense of taste, smell, feel, specifically since its vicarious and immersion by imagination. the hand scratched the itch but without the visual, esp. more extreme or intense scenarios, there simply isnt enough. so you are conditioned to be stimulated visually as a necessity. problem is in real sex your point of view is always first person and limited by your position which may actually be visually limiting but appealing to the other senses. having your head by her neck means taste, smell, feel if your pressing against them, are all elements missing from the pmo equation.

2) optimal hardness for hand activity is going to be something softer since the hand is much harder and less inviting that the vagina. masturbation feels less good with a seriously hard one and may be optimal just shy of max hardness or even softer. since porn makers are often pmo consumers it might explain why in porn itself dicks dont ever seem as hard as they could be. with actual sex however the harder the better since the soft sensitive spots with the vagina benefit more from direct and therefore more apparent stimulation.

a recent session with my wife after a really solid though short stint of no pmo had me noticably harder than usual which was its own turn on for her independant of how much more effective it was. the success appeared linked to the more thorough abstinence, which was both physical AND mental abstinence