Space trash
Humanity, as a whole, has a tendancy of not caring if it doesn't seem to matter. The only problem with that attitude, is that we often cannot see how it matters before it is too late, or at least much more expensive to correct.
That is why we are choking the sea with plastics coming from bags that have been carelessly thrown out a car window, or left on the beach because the trash can was five meters too far away.
In space, it has been the same thing. The entire space industry has, since the beginning, operated on a it-doesn't-matter attitude. Leftover rocket booster lounging around at 600+ kilometers ? Doesn't matter, it'll end up coming down.
Except that, since the decades we have been throwing stuff up there (and given the cost, with pretty good reason, generally speaking), all those remaining objects are now starting to clutter up Earth's orbital space and becoming, if not yet a danger, a clear nuisance.
All of that because of our human reflex. Like the smoker who just chucks his cigarette butt instead of putting it in the trash bin.
We will end up paying for that as well, in time.