if you know how to write decent C, you'll have a much easier time of understanding PostgreSQL internals, for example, while if you've learned React, it's anyone's guess as to whether or not that'll actually improve your HTML skills, for example.

I mean, there's also a much more mundane reason why C comes up more often: It doesn't use a runtime environment, so a library written in C can be called from virtually any programming language.

For the longest time, if you wanted to write a cross-language library, C and C++ were pretty much your only choices.Rust is now entering that circle and I do think, it will start showing up in lots of places, too.

But perhaps another reason why mastering C is more educational than mastering other languages, including Rust: C hardly abstracts from how the hardware works, so you're not just mastering C, you're also mastering hardware.

Other programming languages ultimately get executed on that same hardware as well, even if lots of abstraction layers are in between, so that knowledge still keeps being relevant every so often.