[duskwuff]

Dead satellites and debris in low altitude orbits will experience orbital decay and burn up in the atmosphere within a few years. High-altitude objects (e.g, at GEO) are more of a concern.

[flukus]

Unless some debris from that gets pushed into higher orbits, then collides with something else and the process repeats.

[Symmetry]

In GEO everything is going in the same direction at the same speed so there's really no danger of collision. It's all the satellites whizzing over Earth's pole in different directions that have resulted on the only accidental collision.