I have no idea what you're trying to say. There are millions of people involved. Averages make sense to use.
For example maybe 450k are unable to get a ticket because a plane filled up with non-riders, and 550k are able to get a ticket when they couldn't before because additional capacity was allocated to the route. Is it 'disrespectful'? Hell no, in my view. It's just shuffling what are fundamentally random numbers. These people are buying tickets too late to be assured seats. Some will get them, some won't, and buying your own is not a negative unless you do something like coordinate to buy out an entire route.
Edit:
>I'm not the one considering one single outcome
Yes you are. You are only considering the possible downsides of a purchase. I could use a similar argument to say that nobody should ever buy anything non-critical because stock might run out and screw over the person behind them.
And then the economy collapses.