Or is it perhaps because users don't want to use it unless they have no choice (in terms of software alternatives released under other OSS licenses)? 20 years

Or is it perhaps because users don't want to use it unless they have no choice (in terms of software alternatives released under other OSS licenses)? 20 years ago GPL was the only thing most users new to OSS knew about. Since then they have learned there are better choices Meanwhile GPLv3 was the final nail in the coffin of the bossy OSS licenses. One thing I don't get is why the OP proclaims love for GPLv3. It's the worst GPL license out there. I avoid it as both a contributor and user.