Yeah, I have no idea why Rebol and Red aren't more popular. ( https://www.red-lang.org/ ) They pack such a bang for the buck it's almost embarrassing for other language/runtimes.
Rebol itself is practically dead, no new release in a decade. It was also proprietary early on and a "weird" language (interesting, and good, but non-standard in so many ways that it was very niche). That killed its potential in the late 90s and early 00s when everyone was moving to open source scripting languages that filled the same niche, but with more conventional syntaxes and free access.
That's why it isn't more popular. In some ways it was a few years too early (to hit the zeitgeist around DSLs), but it was also a few years too late for its proprietary model.
And something else that needs to be said specifically about the Red programming language. I like the full-stack concept, ease of use, cross-compiling, and the goals they are shooting for. But, the lead developers need to get it moving. Like a small fire needs to be lit under the butt, as the competition isn't standing still.
The last stable release has been stuck at 0.6.4 since 2018. I know the lead developers have recent automated builds (December 2021), but come on, such is not going to inspire faith in casuals to join the bandwagon nor keep getting mentioned by the media. Many users like to see newer stable releases, until the project achieves its stated goals. A lot is to be said for maintaining momentum and enthusiasm.
That's another aspect of the hurdles for the newer programming languages, it's harder than ever to keep people's attention and whip up excitement.
The problem is that there are so many new languages that it's hard for any of them to gain enough momentum to encourage enough programmers or businesses to learn or even look at them. Not to mention that various top 10 languages are supported by huge companies that may rather snuff out or at least throw shade on up and coming languages that threaten their interests.
The development pace of many of the new languages is relatively slow, despite having some great ideas, syntax, or features. Which means years before they have a large enough ecosystem and libraries, to even come near to mounting a challenge to the more established languages.
For instance, another new one out there that I like is VLang (https://github.com/vlang/v). Like Red, it needs to find a sweet spot that will propel it to greater usage and recognition. Partly that can be cross-compiling and cross-platform application development. Also, strong emphasis on mobile development for both Android and iOS would help, but Apple makes their part of it difficult. To stand out, it means having easy to create UIs, their own IDEs (to maximize language features), updated documentation (to help beginners), books about it, etc... Just being on Visual Studio Code, with a hundred other languages, makes it hard to get noticed.
Compare Red with established heavyweights like C#, Python, JavaScript, or even contenders like Delphi/Object Pascal. Not so easy to pull attention away from those languages and the thousands of projects using them, unless something very compelling can be shown or proven.
> Yeah, I have no idea why Rebol and Red aren't more popular
Rebol died (for all intents and purposes) because it stayed proprietary without a large enough proprietary market too long, and good enough open source languages took the niches it could have had and built out robust ecosystems that it never developed.
Red has been disadvantaged by the ecosystem consideration, and hasn't found a killer focus that gets people over that in enough mass. They tried chasing crypto for that...
Similarly, TeX bakes units into its syntax, but METAFONT (which is much more pleasant as a programming language in general) just has a production for <numeric token> <numeric variable> instead (yes, it has a very involved context-dependent grammar), though it gives up type checking because of that.
Rebol, is mostly "dead", and I don't like to so easily throw the term around. But, originally it started out as a proprietary commercial language, then when it couldn't make enough money, went open source. It has some good concepts, and passionate followers, but didn't go mainstream. Even though it went open source, in the flood of so many languages that exists now, continual development stalled. However, it did produce several offshoot descendant languages.
Something to point out, is there is a lot of old tutorials and information on Rebol that becomes more useful as references, if a person learns any of the descendant languages.
Red (https://www.red-lang.org), is a very good open source offshoot. If a person is choosing between them, I think most would recommend it. But, the problem with Red is its development can be described as sluggish. The lead developers appear overly preoccupied with other projects, as oppose to getting Red into a more useful state and delivering on the stated goals and expected features.
For example, one of its main benefits is easy cross-compiling to other OSes. However, it's stuck in 32-bit, and needs to have a 64-bit version to keep pace with the requirements of macOS, iOS, and Android.
If Red's development was to keep on pace, which is important for multi-OS usability, I do think it would be worth knowing. Quite powerful and easy to learn language, for potentially a wide variety of purposes, with a light footprint.
In reality? None. Both give me lots of trouble. Red doesn't offer a good external program launch, which when things fail, I always drop down to sh. Rebol interestingly enough offers a wee bit more stability. but its age is clearly showing. r3 being open source has a bunch of versions and forks, none of them usable. there's also ren/c which is supposed to be usable, however I cannot build it on a pi4, there is also another attempt which is called arturo, written in nim, this one works but development is only done by a single person.