The proper way to do it sometimes is horrendously complex or uses a build system different from the one you use. Header only avoids this usually.

Building a plain .a/.lib or .so/.dll is not horrendously complex.

Package management is often hideously complex and a central sink of labor effort in linux distros. Building it for yourself is easy, in practice using dynamically linked libraries are the start of all sorts of troubles.

Providing static libraries is also an option.

Generating rpm or deb files is hardly the end of the world, there are even package generators available.

I just watched a cppcon video where Bjarne himself lamented about the complexity of installing many libraries for use in C++.

I’ve personally had great difficulty building these for large libraries, especially when they use a build tool different than the one I’m familiar with (I use cmake for C++ these days but I find cmake itself horrendously complex and difficult to understand even after investing significant time into it).