I feel like like it really took off in the 80's.
All along though there was a group of people who never gave up the mustache.
There is a perfectly good reason why.
This is the best pilot mask I could find.
These two masks have a very important use in common, they keep people alive. They do it better when they have a solid seal on a face. Now I can't speak for the pilot mask, but I know that the SCBA is positively pressurized so if you don't have a perfect seal on your face that you start losing air... and in a fire environment air is equivalent to being alive. That is why you can't have any facial hair around the jaw line, and why pilots and firefighters rock mustaches.
It is no secret that people love firefighters, or idolize fighter pilots.
That, my friends, is why mustaches are cool.
I'll end on a joke that many of you have probably heard:
What do cops and firefighters have in common?
They all want to be firefighters. :)