The entire programming (or even computing) ecosystem suffers from this issue where very useful ideas don't always propagate across domains even though they just make a whole lot of sense. I'm not sure if it's because they truly wouldn't work out in practice, or if it's just a discovery/communication thing.

One thing that I think do affect things, is that language design discussions tend to be concentrated into their own communities based on the programming language itself, rather than one "programming language discussions" place where everyone can easier cross-pollinate ideas across languages. Luckily, there are some individuals who move between communities without effort, which does lead to a bit of ideas making it across, but it feels like we're missing out on so much evolution and ideas from various languages across the ecosystem.

The cross-fertilization of ideas across computer science domains is more limited than I think people assume. Databases are just one area that contains a lot of good ideas that never seem to leak into other parts of the software world.

Supercomputing is another domain that has deep insights into scalable systems that is famously so insular that ideas rarely cross over into mainstream scalable systems. My detour through supercomputing probably added as much to my database design knowledge as anything I actually did in databases.

The canonical industrial explanation “why not” is probably this 2010 piece from Joe Duffy @ Microsoft:

http://joeduffyblog.com/2010/01/03/a-brief-retrospective-on-...

It is a big reason why I picked Scala3/Zio over Rust for my most recent project.

Well, what means to support, truly, TVars?

Is easy, or hard?

Demand a new paradigm at large, or is only a inconvenience in the few places is used?

Because if the answer is "turns the language into Haskell" then is a big NOPE!