One reason why many people keep so close to whatever is up front is that they get fed up with other road users darting in between, as that's what happens all the time on the busy 4 lane highway on my commute.
You have to slam the brakes from time to time, whether you keep a good distance or not.
You cannot always anticipate on whatever is coming two lanes across.
The exception is when following semis at a respectable distance in the slow lane.
Usually nobody gets in between except at on and off ramps, and that too seldom causes problems.
If there is no side wind the draft effect even works at those distances.
There is no such thing as absolute safety on a busy multilane highway, no matter which strategy you take. Keeping a safe distance and being alert helps, but even then bad luck may find you.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
 lifetime FE over 0.2 Gigameter or 0.13 Megamile.

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