Spacex's satellites are intentionally short-lived and have a useful life of just five years. If someone went to the enormous trouble of knocking them all out, SpaceX could just launch a barebones service replacement on the next satellite full of replacements they were going to launch anyways.

Honestly, part of why I'm reluctant to commit to using Starlink is because it sounds like it has very high operating and maintenance costs for that reason. Sure, Musk has made space launches cheaper. Cheap enough to intentionally use short-lived satellites for long-term static services? I don't know....