So many things to disagree with, so little time... where do I begin?
Anywhere, I suppose, and then just run off in all directions at once, hoping that in the end it all comes back together. So in no particular order, here's what I think.
First off is that we're talking about way, way more than just complainers and FF benefits. While I understand the sentiments, so many of both the original poster's points as well as others added later are about things that actually live in different worlds. So different, as I used to say way back in a Calculus study group, that we're comparing apples to rabbits.
With regard to the complaints and/or complainers, regardless of the complexity of the operation, any time someone complains it means the organisation has in some way failed. Perhaps the complaint isn't actually justified, but what was the origin of the passengers expectation in the first place? And as someone else has already well demonstrated, airlines are the masters of creating unsupportable expectations. Airlines have taken everything they could conceive of from the days when award flights were "free" and every flight meant a meal, and either eliminated it or begun charging for it.
As well, airlines are notorious for loudly and widely proclaiming "improvements" (no matter how insignificant) while at the same time suppressing notice of cutbacks in service and increases in fees for as long as possible, which usually means until they are caught out. Many have noted (and Air Canada sometimes brags) that they are a leader in this regard, though they may not couch it in those terms.
Beyond the complaints themselves are the airlines apparently immutable inability to deal with them in a way that satisfies (at least) most complainers. Several years ago when asked how many complaints a year each airline received, most replied "none of your business." An exception was British Airways that almost bragged that they had 200 people who dealt with about 300,000 complaints a year, and considered everyone one of those complaints an opportunity to improve. Fact is, no matter what is wrong, nothing... nothing... gets "fixed" until someone complains about it. If it wasn't for the complainers, we'd still be trying to figure out how to keep a fire alive.
{more to follow}