Some of the time, that is true, but not all the time, maybe not most of the time -- you are putting the cart before the horse. In fact, I would argue that this is an anti-pattern. Yes, you might use (e.g. to pick 2 unrelated domains) Hadoop or Python because they are popular, but consider how they got popular in the first place.
Devtools exist to solve a problem. You should not evaluate devtools based on the webpage or how many people are using it. That way lies Oracle enterprise. :-)
The problem with Docker's website is not that it exists. It is that it substitutes sales & marketing for just simply explaining what it is to a developer. While one could classify this under the category of "marketing", it would be a mistake -- kind of like classifying man pages as sales pitches. Just tell me what the fuck it does for god sakes and I'll decide! I could give a rats ass whether Facebook uses it, etc...
To be clear, I find Docker, the tool, useful, I just think it doesn't need "Marketing", it needs a useful webpage.[1]
Ruby was not adopted because of its webpage or its user base, it was adopted because one person bothered to look into it, liked it and decided to build a very popular web framework around it. Others saw the value in that domain and it exploded. Similar situation for Linux, which started from an FTP site and usenet posting. :-)
"The nerd-centric viewpoint that tool should succeed entirely on their own merits, with no affordances for the user, is crazy."
Unrelated to what I was talking about entirely. Affordances to the user is a merit of the tool itself. Docker could be considerably easier to use in some regards, and that would improve it's usefulness as a dev tool. However, this has nothing to do with attempting to gain marketshare with no direct relation to merit.
[1] But then Docker, the organization, is selling something, aren't they?