You're partly right but autoconf's design is pretty rigid. I've never seen one where the install destination isn't set via one of the standard flags like --pref

You're partly right but autoconf's design is pretty rigid. I've never seen one where the install destination isn't set via one of the standard flags like --prefix. But I have seen other build systems randomize their install processes. Maybe this is a function of what kind of people use each tool. Autotools is mainly adopted by experienced geeks. Other build systems are more beginner-friendly and that might result in less appropriate solutions being written.