List of reasons something isn't popular or successful

(i probably need a better title for the thing i am trying to point to)

For a few different values of interests X, I often have thoughts like "Why isn't X more popular? Why doesn't X have a community around it? Why aren't there people getting paid to do X? Why is Y a thing when X isn't?" I want to understand this better, in particular by listing out reasons this can happen.

• from this comment by Eliezer Yudkowsky (for anywhere with a stream of rent/where gullible people exist):
  • heavy competition
  • barriers to keep out new entrants
• considering things more narrowly on topics I care about (e.g. it's true that math itself is pretty popular and people do get paid to research it. it's just my kind of math that is completely unknown.) Whereas for something like mountain climbing or meditation, I am an outsider so everything blends together.
• I have higher standards (e.g. "be able to make a living doing X") for my interest and lower standards for other interests, e.g. probably none of the mountain climbers in the scenius article (see also scenius) were getting paid to do it.
• X requires expertise in many different domains, so there are very few people who are qualified to work on it.