Rather than indulging the inevitable argument that most users never read log messages, I hope we can remember a more important fact:

Some users do read log messages, just as some users file useful bug reports. Even when they are a tiny minority, I find their discoveries valuable. They give me a view into problems that my software faces out there in the wilds of real-world use. My log messages enable those discoveries, and have led to improvements not only in my own code, but also in other people's projects that affect mine.

This is part of why I include a logging system and (hopefully) understandable messages in my software. Even standalone tools and GUI applications.

(And since I am among the minority who read log messages, I appreciate good ones in software made by other people. Especially when they allow me to solve a problem immediately, on my own, rather than waiting days or weeks get the developer's attention.)