Because of type safety. The OTP lib is already great, but there are still some things missing, most requested being named processes. But there is work being done to figure out how to best make it work for gleam.
The question of type safety has come up so often here that I guess it's worth replying:
That's exactly what I mean by this not seeming pragmatic. Pragmatic would be making do with partial type safety in order to be fully compatible with OTP. That's the much-maligned TypeScript approach, and it worked for TypeScript because it was pragmatic.
Now, maybe Gleam feels the need to take this approach because Elixir is already planning on filling the pragmatic gradually-typed BEAM language niche. That's fine if so!
Type safety is one of the goals of the language I don't see a reason to throw it out of the window now. I see what you mean, but the type system is one of the things that makes gleam pragmatic. If you really need some missing OTP feature you can super easily step into Erlang using FFI and get it. That's one of the reasons the article doesn't call gleam pure.
And what has this approach gotten them? A language as complex as c++ and haskell combined, but that still has runtime type errors. A typescript backlash is coming.
That's exactly what I mean by this not seeming pragmatic. Pragmatic would be making do with partial type safety in order to be fully compatible with OTP. That's the much-maligned TypeScript approach, and it worked for TypeScript because it was pragmatic.
Now, maybe Gleam feels the need to take this approach because Elixir is already planning on filling the pragmatic gradually-typed BEAM language niche. That's fine if so!