[derefr]

Every opinion piece can be rephrased this way. If someone believes in something enough to tell others to do it, they very likely also believe that thing enough to put it into practice themselves.

You'll only hear about the advantages of, say, git, from people who use git. Does that mean they're telling you about git in order to get git some more market-share, so that development effort will be even more concentrated on it? Probably not; they probably just think git is a good idea, and therefore use it themselves.