An element of this is that your porn collection is kind of non-physical, or all condensed onto a hard disk inside your computer somewhere. So porn pops up on the screen and people think 'oh big deal everyone has porn now'... but imagine if each of your movies was a physical DVD, in its full case. So you might have a massive bookcase full of these DVD boxes, all lined up filling an entire wall of your bedroom. THEN, people would be shocked and you would feel weird about it. People would walk into your room and go "Jesus Christ Squallmuzza look at all the porn DVD's you have... you need therapy!"
Well this is the case for me anyway with about 300GB of porn. But when it is all invisible and all compressed down to a tiny little disc inside your laptop somewhere... it seems like no biggy?