It's like anything else. Many guys have a hammer in their tool box. They don't always use it, but if they need it they have it (and works well in certain instances). Others guys use their hammer way too much and do more damage. Social media is the same way. Used correctly a great tool, used incorrectly and it can cause more damage than it fixes.....
Some don't use social media because they have something to hide, others don't have anything to hide but don't use it because they don't like the big brother effect, and some others don't use it because they just don't have time (or the know-how).
I've set up Facebook, Twitter, Instagram, etc for my parents (both in their 70's) just so they can keep up with their Grandkids. They never post, they just follow and it's a tool to keep them in touch over 3000 miles away (California vs Massachusetts).
Good or bad social media (in one form or another) is here to stay, because of that I try to make it work to my advantage. Their is a TON of BS, but I've also learned a lot and met many good people (much the same way the forums helped in the late 90's early 00's).
Some of the first boards I belong to (mostly for square bodies) didn't even have the option to post pics....you actually had to describe and visualize problems.