Here's the joke: Why did humans invent language? So we could complain! (Ba-dump-chick!)
Like the best humor it's funny because it's true—or, at least, it carries a sense of "truthiness." Even conceding that communication serves more of a purpose than merely that, there's little quibbling that we have more language than is necessary for merely the utilitarian purposes of living in groups.
On the surface, a complaint suggests a desire for change, for the focus of that complaint to be addressed so that it is no longer a source of frustration or annoyance is no longer so. That's not the case, however; complaints are the means of dispersing the frustration or annoyance so it's not so personally bothersome. It's venting the proverbial steam that builds up from having to deal with a world filled with sources of frustration and annoyance. That's the sum total of what the complaint achieves.
Oh, certainly there are times when someone may take action to address the situation, but that's more of an indirect connection. What's desired is to make that particular complaint cease. And the change comes from the action; the complaint, in and of itself, did not change anything other than perhaps reducing the blood pressure of the person who complained.
Which is all that is really wanted anyway.
If there's one area in the human experience that is truly limitless it is the capacity to find something to complain about. Even if every single issue that annoys you at the moment were magically resolved precisely to your liking, tomorrow you'd have a whole new slew of sources of frustration.
Ostensibly complaining is about what makes us miserable, but in actuality without anything to complain about we'd be miserable; only by being bothered enough to employ our developed language to complain can we be happy.
And if you don't agree, you're certainly welcome to complain about this (there's the Comments link below). I'm sure it will make you feel better.