I get why this practice is upsetting, but people might be doing it for the right reasons sometimes. I, myself, prefer to keep my relationships private. Why? Well, because:
1) I want to enjoy it myself and not listen to others offering their opinions.
2) when you keep it private, you don’t “invite” others into your love life.
3) if you have somewhat of a judgemental parent, like I do, you can “protect” your relationship from scrutiny.
4) you don’t invite anyone to your bed and sex life either. No one should stick their noses into that.
5) you protect yourself from other people’s expectations, ideas, perceptions and many other things which have NOTHING to do with your own.
I should state that I’m a committed partner, not someone who tries to hide boyfriends from others. But I want my love to be between me and my partner, not 20 of our friends and family or 1,000 people on the Internet.