I don't think there's one real reason but a combination, but I can list the features that C# and Java ecosystems had since the early 00s, and javascript/Rust ha

I don't think there's one real reason but a combination, but I can list the features that C# and Java ecosystems had since the early 00s, and javascript/Rust have since they came around, but C++ hasn't had until recently. 1. one or more major package hubs 2. one package manager, or at least, a package standard 3. easy to consume/build (source code to binary) 4. easy to publish 5. easy to download (one liner in your build script, e.g. package.json, vcproj, cargo.toml, build.gradle etc.) At the moment C++ only really has 5. - easy to download: cmake, conan, vcpkg, build2, can all download easily. 1-4 are a work in progress for C++, but are far better than 10 years ago.