Look up the "Gabbard diagram" of any orbital collision. Some of the debris ends up in rather elliptical orbits, with an apogee considerably higher than the orbit of either object that went into the collision. That means it presents a risk to satellites even in higher orbits.

Also, orbits decay. The atmosphere doesn't just stop at a line; there's thinner and thinner wisps of gas out there, ever so slightly dragging on orbiting objects. So higher orbits slowly get lower, and lower orbits rapidly get lower still, until the orbit turns into an entry trajectory.

The properties of the exosphere are fickle and change rapidly, influenced by the solar wind and other forces. So while it's certain that orbiting objects experience drag, it's very uncertain how _much_ drag.

An object in an elliptical orbit spends some of its time with a very low perigee and thus a lot of atmospheric drag and thus its orbit changes rapidly in ways that're hard to predict, even if its apogee is high enough that it also crosses orbits of interesting things that're trying to avoid it. And the less predictable it is, the harder it is to avoid.

2) Setup shadow satellite corporation

3) Satellite corp launches satellite to valuable orbit, and intentionally separates into 2-3 easily caught pieces. "Oops! Our satellite failed"

4) space debris company cleans up the orbit quickly and easily, receives bounty from government agency

5) Profit

A little far-fetched maybe, but there's a good sci-fi short story wrapped up in there.

There's thankfully a very obvious repercussion to leaving stuff in orbit that anyone planning to put something in orbit can see in obvious ways, unlike the delayed and hard to account for impact on the climate any one company will have.