As I mentioned, not everyone has an open-minded family, a trustworthy spouse, or obedient children. Or even a personal PC that no one touches. It's not a matter of being morally wrong to snoop on someone's PC, it's a matter of evidence (legal or not) that can get you into deep trouble - or, in the case of a divorce, cost you much more than your house.
If someone in your circle could snap out upon learning that you watch porn, it means that person is already extremist enough (or vindictive enough...) to prioritize morality or his own interests over your well-being, or even your life.
Every day, you can read tragic news stories that support what I'm saying. If you're lucky enough to be outside such an environment, like me, that's great. But others aren't so fortunate.
Don't mess with crazies, you always come out the loser.
Jokes aside, hiding porn might make some people smile. However, everyone has something to "hide", I guarantee you that... Not because you're "ashamed" of it, but because no one should be able to access it - your scans of important papers, at the very least, which could allow any ill-intentioned person to completely impersonate you, and therefore get you into unimaginable trouble.
And whatever you want to protect (or "hide"), what has been said here remains valid and will allow you to protect them either minimally or reliably, depending on what you need.