It's not even about being old, but having different versions. Take libcurl and OpenSSL for example. Some distros use OpenSSL 1.0.2, some default to OpenSSL 1.1

It's not even about being old, but having different versions. Take libcurl and OpenSSL for example. Some distros use OpenSSL 1.0.2, some default to OpenSSL 1.1.0, in some cases libcurl depends on 1.0.2, but the system in general prefers OpenSSL 1.1.0. Which one should you use in your application for crypto? Obviously, the sane decision is to provide a separate build for each distro which uses the libraries bundled with the distro. Or you can just link everything statically (and then security updates of OpenSSL become your problem). Then also come QA people and management, which want to support multiple distros, but do not want to support multiple packages (as they are different and require separate QA effort), plus the users would find it hard to install an appropriate package for their distro. So... it's more convenient to just link statically.