Good luck maintaining a safe distance on a busy highway when every time you slow to make a space, somebody moves into the space from a different lane.
It's a different situation when someone is slamming on their brakes from highway speed with nothing ahead of them.
1. It's the fault of the driver behind, for not leaving space
2. It's impossible to leave space, because cars will move in if there is a large gap
3. Why is this a problem?
"To keep a smooth traffic flow, some highways also have minimum speed limits. If you drive slower than the minimum speed you can halt the traffic flow and create a dangerous condition. Even if there is no minimum speed limit, those driving too slow can be as dangerous as those who drive too fast."
https://dmv.ny.gov/about-dmv/chapter-8-defensive-driving#yre...