No, it's not unique. You should see the emotional attachment that some regular returning passengers have to their favourite cruise line(s), and how angry they get when they realise that the company doesn't feel the same emotion towards them.

I think that the common thread is that individual purchasers see an airline ticket as a (if you'll pardon the phrase) "big ticket item". They put a lot of thought into the question of whether and where they're going to spend several hundreds or thousands of pounds, and they think that they should therefore get an emotional and behavioural return from the company (eg "oh, you've splashed out so much money that we must reward you with a free upgrade") in addition to the supply of the purchased product. This is why nobody expects it from a train company - to the passenger, the outlay is small and nothing extra is expected.

But the reality is that normal fares are, on an individual basis, almost trivia to the airline. Getting revenue and making a profit is more a big numbers game, and no specific individual ticket is that important. Hence the vast disconnect between some passengers' expectations ("Well, I spent a huge amount of money") and the ability or willingness of the airline to provide extras to just another ordinary item of fare-paying self-loading cargo.

Ultimately, for the company, encouraging the emotional attachment called "loyalty" is a good way of increasing future revenue and (hopefully) profit. So, like others, I don't understand why these two concepts should be regarded as mutually exclusive. They're both part of the same behaviour that the company is trying to generate - reliable repeat future sales.