> I will never understand why this is so rage-inducing for people.

The train of tought goes something like this. You want to get to your destination quickly as just like everyone else and are doing everything correctly, but the assholes exploit that safety distance as a gap available for them to switch into and repeatedly forcing you to break to maintain a safe distance. Oh and the even less rational people think everyone overtaking them has stolen their rat race position.

Leaving a keeping a safe distance feels unsafe since other drivers will squeeze into it. Subjectively it feels safer to close the distance, but the numbers don't lie. Tailgating kills.