When it comes down to the sexytimes, whether you have a partner or not, the last thing you need is someone disturbing you. Doesn't matter how. Whether it's your friend texting you memes, someone walking in on you in a compromising position, or any number of things like that. YouMode may be a tool for the budding masturbater, but it could work in all sorts of other situations too.
So it's designed to keep people occupied and not worrying about your lack of response time, and to stop people from walking in on you mid-wank. Then again, who says this all has to be about wanking? You don't want to be disturbed by some inane things if your date went really well, and you certainly wouldn't want the kids barging in when you're in the middle of having some 'alone time' with your spouse. It's all a different kind of embarrassing and irritating than if you were caught by yourself, but that doesn't make it any more pleasant.
So YouPorn? Make this happen. If your parent company can make age verification gates, it can probably do this. Thousands of teenagers will thank you one day.