Actually just got done benchmarking this. The conclusion was that it is a worthless optimization compared to just sending the client a gzipped webpage without minifying first. https://github.com/yeoman/generator-gulp-webapp/issues/215#i...
What your benchmark shows is that gzipped pages may be as much as 20% larger than minified + gzipped pages. Even larger pages typically were 3-5% larger.
Sometimes you'd kill for a 3-5% improvement.
I would agree that it's not the most important optimization early on, it's probably not even worth doing at all unless either it's trivial or your project is big, stable, and consuming tons of resources. But that's not the same as worthless.
It's also the case that mature tools (from your compiler, to SQLite, to your browser) chase "worthless optimizations" all the time. Front-end development is in such a state of flux that we don't expect our tools to do that. But eventually we will.
"Worthless" is just too blunt of a verdict.