I have once, in the past year. I used my professional flat iron that I spent way too much on 10 years ago. It was the only one that would actually straighten my hair. I also used the chi flat iron spray.

I only did it because something about my cut seemed off. I wanted to check the even, or unevenness. Straight is in no way a flattering look with the short cut I now have so I washes it the next morning.

When it grows out I will probably straighten it, from time to time. It's always been a rare occasion for me.
When I hear terms like "hipster" I think, who told cliques they could leave high school??