If you think of the last 10 flights you were on, how many had the gym sock smell? That's the real occurence rate. I'd say in my experience across all airlines its around 7/10 flights I can detect via smell a fume event.
If anything smelled it's usually due to a passenger. But nothing from the aircraft itself
Politely, I don't believe you haven't noticed the smell - this statistically is impossible when at an airport with multiple planes. You can smell it daily, at any airport terminal of your choosing, impossible to ignore when closer to the gates. It's a smell powerful enough to not get eaten by the various encapulation, ozone generators, and air fresheners used in public commerical environments like airports. The smell comes through from the planes and gangways into the terminal itself.
Next trip: With a clear nose, smell the air at the airport entrance and then compare this with the smell closer to your gate. The contaminated airs smell it's very similar to a wet locker room or gym bag that was left for days without cleaning. You won't ever miss it again, and your stat will flip to detected in 50 out 50 visits.
Since airlines consolidate on specific types, it is possible that some travelers experience this problem often and others very rarely.
Through no choice of my own, I seem to only fly on Boeing 737s, but the one recent time I was on an Airbus (A321neo) there was a distinct exhaust odor upon engine startup.
Coincidentally, when I am flying anywhere in Asia, I get none of this. I'd unironically rather be on an Indian airline for most flights because for all the flack that Indian people get about cleanliness, they're far more likely than the average gringo to have used a bidet at some point in their lives.
Even in a perfectly working bleed air system, the air comes from outside the plane, which on the tarmac of an airport, is god awful, shitty, and not at all healthy.
Lot's of other commenters talking about how the smell goes away at altitude.
Because it doesn't come from the packs (except in fume events), and what people are usually smelling is that airports have very bad air, and that air is much cleaner at 30k feet.
The miniscule oil vapor/droplets that are making their way into the bleed air system from engine compressor seals will still happen at 30k feet. If you don't smell something at all times on a plane, it cannot be coming from that.
This level of contamination would be like working at a gas station, which can be a health hazard. OSHA regulates air quality for employees working around hydrocarbons.