While I sort of agree with you, I'm a software engineer with a background and hobbies in the arts. My wife and I are part time performing magicians, and I used to play various instruments in rock bands, I produced an indie album a few years ago etc. I'm saying this because I hang around people who are hyper-creative.
I compare those hyper-creative people to other people that I know and I work with and it becomes very apparent that what we tend to think of as "creativity" is not something that even the majority of people possess.
I definitely agree that everyone is "creative" to an extent within their respective interests and productive pursuits. But I think we might be conflating creativity with productivity. Everyone produces, or at least is capable of producing things. But what we tend to think of as "creativity" involves abstract thinking and piecing together things that are non-obvious.
In that sense, hackers and engineers do tend to often exhibit this form of creativity. I mean using something in a way that it was not original intended is an example of that "outside of the box" abstract thinking.
But my point, as anectodal as it is, in my 40+ years on this planet I've encountered far more people who are incapable of abstract thinking and coming up with novel ways to combine things than I have people who do possess this ability.
Now it might be a muscle, it might boil down to interests and personal ambitions. But, and I think you'd even agree with this, that's a hypothesis. I don't personally see evidence in support of that. The people who can't think abstractly are even some really decent programmers that I've met. They can produce shippable code and solve problems, but they can't think in terms of design patterns and abstractions... they need concrete examples for everything. The second you start to abstract a solution and talk in terms of generics you lose them. And I'm not putting them down, they're still great people to have on your team. Great work ethic and love what they do. They just can't think abstractly and are therefore not "creative" in the way that I interpret that word.