Comment by pjmlp

Just like many C code bases are stuck on C89, many Python in Python 2, Java in Java 8, .NET in .NET Framework,...

Not that every compiler is up to date, but at very least clang, gcc and vc++ have already quite good coverage of C++20, and clang/vc++ modules mostly work, good enough that I only use modules in my hobby projects.

It starts by projects, companies, actually wanting to adopt new toolchains.