The trend I've seen with web development is that it's mostly a primary skill. While data science will be a primary skill for many, it has the capability to be a much sought after secondary skill in other industries like finance, health, and actuarial science.
Where are you seeing all the demand?
Working in advertising tech, we'd be looking for someone to join the team on a permanent basis. Even with data science fundamentals, you have to marry that with a thorough understanding of the industry to develop that productive intuition about how to help folks solve their data problems.
True, but HN is not particularly representative of computer science or software engineering related fields (well, it is, but only a small percentage). There's a lot of stuff going on out there both in industry and academia that doesn't make it here or get particularly represented in the jobs/freelancer threads.
You need a degree or relevant past work to land those jobs though.
There are also companies that you would work for that would provide these services rather than being hired or contracted by the company directly. (like SAS)