If indeed they were speeding to a ridiculous degree, and it was a safety issue, and it caused them to be at fault in an accident --- some silly license plate frame is not going to get them out of it, or protect them from the multi-million$ personal injury lawsuit from the impacted driver.
Which, I'm sure, is a great comfort for that now-crippled or -deceased driver. The guy with the license plate frame is probably very sorry after the fact, and would probably do things differently in retrospect. Meanwhile, the guy who lost his legs doesn't want a million dollars; he wants his legs.
In occupational health and safety, it is generally and widely understood that serious or fatal accidents seldom occur out of the blue. A fatality will nearly always be surrounded in time and space by a cloud of (usually unrecorded or unreported) near misses and minor incidents. Relatedly, there is the concept of "normalization of deviance". Essentially, the idea that if you let your standards slip a bit and nothing bad happens, the tendency is to allow that lower level of vigilance to become the new acceptable standard. Lather, rinse, repeat until a major failure occurs. (The Challenger disaster is an oft-cited example.)
Coming back to the licence plate frames, I don't care whether or not someone gets a fine for speeding. I do care that we've created a pool of privileged drivers who are no longer receiving any feedback when they engage in higher-risk driving behaviors. "Go ahead and drive as fast as you want; we'll trust your judgement on that until after your first high-speed collision..." probably isn't a real solid basis for road safety.