In my experience, branching has only been mainstream since git became popular a couple of years ago. Before that, when using svn and other similar systems, branching per feature was unlikely in my experience and a major pain.
Branching is very well supported in Subversion. There is a reason feature branches occupy a large part of the SVN Book.
I would say feature branches were mainstream usage of CVS too, but SVN made it more popular because merging is more effortless.
Github probably popularized it, because they put a web interface on it (which is great), but that can be said for a lot of things.
Give it a few years and everybody will use feature switching, except the old man enterprise dev :)
There are a million things that feature switching let's you do. Enable and disable instantly, enable for .00001% of the users, integration test different combinations, etc.
https://secure.phabricator.com/book/phabflavor/article/recom...