Sometimes people focus their frustration on small things because the big things are either too big or too abstract to express frustration about. Everyone has something in their lives that's difficult or painful, but they're not always things people feel comfortable venting their unhappiness about.
There's also the issue of reliability and expectation. People have come to rely on certain things like Apple releases or whatever because there are so many unreliable things (important ones, like health and finance and opportunity and love) in their lives, and they expect those things to remain reliable. When they prove to be otherwise, it's upsetting.
I take your point, and I'm sure we can definitely come across as a bunch of petulant and spoiled brats, lol. But I think it helps to remember that this is a) only a tiny fraction of what anybody here says or does in their day, and b) a rare place where people feel comfortable being completely honest about the depth of their disappointment or excitement.
At the end of the day, it's just an outlet for people, and that's not such a terrible thing.
