I use social media to learn/sometimes teach, inspire and be inspired and for the friendships. Actually, that really applies only to this message board! On this board there is more give and take. On other forms of social media I am usually taking, though I do try to leave comments on blog posts and thumbs up on youtube videos I like.
Twitter and Periscope - nope
Youtube - I love to watch stamping videos. I don't post videos.
Facebook - mostly joined so I could see my kids' pictures. I rarely post. I find some company pages hard to read. Too many columns.
Blogs - I used to blog hop more than I do currently, and like April mentioned, I started a blog long ago so I had a place to post a project for a challenge (I think for OWH). I like blog hops, but they can really suck up time. I don't read blogs regularly any more, just occasionally.
Pinterest - a little too much! I don't post any of my own cards, but I pin recipes, cards, techniques, wedding ideas
I haven't been asked to post to Pinterest but I did take an online class where inpiration was posted to a Pinterest board as a resource.
Instagram - I have an acct, again for an online class ... I don't really use it or look at it much.
Message boards - almost exclusively here. Occasionally I look at splitcoaststampers for inspiration and technique videos.
So I guess to answer your question, finally, haha, I do use social media for all of the reasons you mentioned ... inspiration, to stretch me to try new things, just for fun, commaraderie ...