Why does the number of people interested in Creative Commons is way less than people interested in Open Source?

I think because CC is inherently not recommended for software

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- I’m not sure I understand what your question is then. Open source pictures are practically the same thing as Creative Commons. The thing is “open source” means the source is open. Why would you need the source for a picture opened if you’re already freely distributing it? People add licenses to things like code so later people can build upon or take parts of in an orderly way. But if you just wanna share your photo to the world online, you will.
  
  FOSS code explicitly states what it is to not be a nuisance to the creator getting requests to fork/modify accordingly. Most people just rip a picture off the internet and use it. Unless it’s for educational/business purposes where they just want a license as a CYA for them.

I think, it's mainly a matter of the works to which Creative Commons is typically applied, being less suitable for collaboration. You might occasionally see remixes, but that's mostly it.

In the case of open-source, collaboration is what elevates it, and often makes it better than paid-for software.
You rarely see Creative Commons works that outdo paid-for works in terms of objective quality. Heck, chances are that more collaboration happens in paid-for works, because they can hire an editor, a sound engineer etc..

Wikipedia is under a Creative Commons license.
- Yeah, solid counterexample. Wikipedia and other Wikis have a clearly defined goal, i.e. collect factually correct information about a specific topic, which is also a goal shared by enough people to drive collaboration.
  
  Another cool example is the Mutopia Project, which basically archives sheet music. Contributors can just pick a piece of music and transcribe that, and they kind of don't even have to talk to anyone for the project as a whole to benefit.
  
  But then there is lots of examples, like writing a new song, writing a new novel etc., where the goal is not clearly defined, where it's difficult to collaborate, because what you contribute might not mesh well with what the others provide.

Because a well done, complete code project benefits more from continued small additions than a well constructed, complete story.

Is that premise even true? This feels like begging the question.

There isn't an inherent financial reason for contributing to Creative Commons work the way there is for Open Source.

Major companies will contribute some development resources to Open Source software because they will get a concrete benefit and the overall effort will be cheaper than going with a closed source option. There really isn't the equivalent for Creative Commons media.

Creative commons is pretty big in 3d printing (arguably it shouldn't be, there's open hardware licenses that are better suited for it).