There is a hidden detail that's worth mentioning about C and C++ style includes: Because compilation and linking are two separate steps, the definitions (included from header files) and the compiled object code that implements those definitions can be kept strictly separate such that you could have two different implementations of the same definitions that are switched in at linker time, for example as a way to provide mock implementations of a specific compilation unit for a unit test, by modifying which object file is passed to the linker.

In some languages this is harder to do as it would require some fiddling with the classpath (in Java for example) or designing with dependency injection in mind from the beginning (inversion of control).

I'm not saying it's a killer feature, but it's something worth noting nonetheless.