Unfortunately the annoyance factor pays dividends for some and that is why they persist in it. But you do find by and large people who habitually complain stress themselves unnecessarily and don't get the best of anything. You just don't bring out someone's compassion, understanding or thoughtfulness by complaining at them.
We all get irritated by little unavoidable things (slow queues, don't get the seats we want etc) but you've got two choices. You can decide its a small irritation and not get worked up about it, thereby having a better day. Or you can ruin your whole week over it by huffing and puffing, rolling your eyes and feeling extremely put out by every small thing.
This is life, stuff like this is going to happen often and if you decide to feel personally victimised and want compensation everytime it does happen you'll have a very unpleasant life.
Upgrades happen, but they are rare and are just someone's good luck if they do. If it happens to you sit in the seat, enjoy the experience and tell your grandkids about it for the next 30 years. Appreciate the fact you got something for nothing, that's rare in life. However, there is no way to ensure you continually get upgraded for free and nor should you expect it. If you want to guarantee yourself that experience then pay for it. It's not as painful as you think it is.
Sorry it's a little off-track, but I was inspired by the previous post to go there.