In London for four days recently, and on the tube - which mandates masks for all - I would estimate that almost no young people bothered wearing masks, (I wore mine).
That's because you're not young!
I use the public transport system on a regular basis, where it's too far/time consuming to walk etc, and the number of mask wearers has plummeted since the summer just gone. Just about every person under 20 maskless and a good proportion of adults of all ages likewise. It makes you wonder what's going on, both in transmission/infection rates in the real-world and in the application of mask rules. I wear one on transport and the odd time I'm in crowded/enclosed spaces, just good practice to my mind.
The longhaul airlines will need to alter the mask rules (with/through govt regulators) if they hope to get passenger numbers anywhere near previous levels. As it stands it will just be business and family obligated half-filling their cabins.