Amusingly enough, though I didn't witness this and can't verify he was telling the truth anyway, my ex-wife claimed that when she went to traffic school, the instructor there told the class the number one cause of traffic accidents on Texas highways was cars going too slow. But I suppose you could argue it's really the opposite even in those cases, that all of the people cutting you off, deciding to get onto a highway doing 20 MPH, doing 40 in the passing lane, or randomly slamming on the brakes because they get spooked by a plastic bag or something, wouldn't be causing accidents if everyone else was also driving really slowly, and the accidents that did happen would be less deadly.
Although, as far as I understand, fatalities on highways are somewhat rare anyway, with most vehicular deaths happening at intersections. After all, it's the stopping force that kills you, and two vehicles doing 80 and 60 in the same direction will collide with less force than one doing 40 and one crossing the path in a perpendicular direction, or two going 20 and hitting head on.
A ton of highway accidents are people changing lanes going way under the average speed of traffic. If everyone was going about the same speed there would be fewer accidents. If everyone is going 75mph and you decide to go 40mph, you're putting yourself and everyone else on that highway in more danger than if you just went 75.
But the accident won't be "your fault" if you're hit from behind and that's what matters more in the minds of those people. It's the Principal Skinner "everyone else is wrong" attitude in real life.
As someone who used to drive a very slow commercial vehicle I absolutely cringe at the people who voluntarily fail to keep up with traffic. It's just not safe and if you're looking in your mirrors you can see all sorts of stupid happen in real time. All sorts of people cutting each other off and getting in each other's way happens as they merge to pass you. All those interactions are potential for something dumb to happen and they are needless.
Although, as far as I understand, fatalities on highways are somewhat rare anyway, with most vehicular deaths happening at intersections. After all, it's the stopping force that kills you, and two vehicles doing 80 and 60 in the same direction will collide with less force than one doing 40 and one crossing the path in a perpendicular direction, or two going 20 and hitting head on.