I know a couple single girls, one is 26 and the other 31. Both have had relationships with guys that they have kept secret from just about everyone. I am wondering if this is a common thing?

I've known these girls for 10+ years, and we are good friends, but they tend to be dodgy about boyfriends, keep things on the down-low, or just outright lie.

For instance, the older chick was seriously dating this one dude for months without telling any of her friends about it. I'd ask her out on the weekends (just friends --group outings, etc.) and she would be like "I might be available Sunday" (implying she had other plans for Fri and Sat). She eventually let is slip to one of her female friends that she was seeing this dude, but didn't give details.

When I finally asked her about him, she said she met him in November (2 months earlier). Turns out, she was dating this dude for 5+ months. Why lie?

Now she has been with the guy for almost a year, and still hasn't changed her FB profile to say "in relationship". There were absolutely no pictures of them together anywhere in her social media, or mentions of the guy. Finally, 8 months in, a picture appeared with them together on someone else's feed. When a FB friend asked "hey, is that your boyfriend? He is cute"!, she didn't respond, but a couple days later simply "liked" the comment. No formal acknowledgement.

This same girl also outright lied about being involved with another guy a year or so before.

Like why do this?