In my experience. I've run into the issue quite often. You find some library, it has its own build system (meaning not the one you're using). It has special rules etc... Integrating into your build system is time consuming and frustrating. Compiler errors from includes, linker errors, etc..

None of that happens with a single file C++ library.

Yeah, and?

There isn't a single build system without issues, other than siloed languages without language standards.

Header libraries only started to be a thing when scripting generation educated in Python and Ruby during the 2010's turned into compiled languages.

That's... definitely a way to describe Sean Barrett, whose excellent libraries popularized this style.

Or among those who want to support any build system

We managed during the last 20 years just fine.

And what build system do you recommend the entire ecosystem support? Well, I choose (arbitrarily different and incompatible one to prove a point). Do you see the problem?

I see a learning problem, because there is hardly a programming language in widespread use using a single one.

And if you're going to point out Go or Rust, it kind of works as long, nothing else is used, and they don't need to interact with platform SDKs.

Everything is easier with single file headers. This idea that a build system and single header libraries are mutually exclusive is silly.

You can take multiple single file libraries and put them into one compilation unit. Then you have minimal files and minimal compilation units. Compilation is faster, everything is simpler.

What is silly is pretending everything is a scripting language.

I don't know what that is supposed to mean and I don't think it means anything.

I'm talking about real pragmatic benefits and you're making some vague hand wavy judgement without any tangible explanation.

I wrote a mildly popular header only library with exactly this pattern once. Then there came a guy adding cmake. I didn't really know it back then so I didn't stop him. The downloads went to literally zero lol. Cmake is an extremely vocal minority.

Who said anything about cmake specifically?