A large part of the answer is because many drivers drive on interstates that were designed for 75 mph speed limits, but are posted at 55 or thereabouts. Many are also old enough to remember the NMSL, which artificially limited legal speeds well below roadways' design speeds. So many drivers have been unintentionally trained to regard speed limits with skepticism, or worse.
Also, it is actually impossible to crash due to speed alone, without violating at least one other rule of the road. Lazy cops cite speed as the cause of almost all crashes, but that's because they are constitutionally opposed to thinking and/or working. So, technically anyway, speeding is safe if the driver can manage to obey all the other rules.
In addition, back in the 1970 envirowhacko days of "68 F and 55 MPH are my limits," there were hysterical projections of what would happen if these parameters were modified or
horrors, eliminated. Much the same howling accompanied the arrival of speed control technology (led by, if you can believe it, the
KENNEDYS! ).
You are correct that speed is almost always suggested as a factor, much as CoVid was blamed for almost any and all deaths two years ago.
In the USA, 40% of pedestrian deaths involve an intoxicated pedestrian.