You don't get it. When car's travelling at 75+ mph collide with semi- stationary vehicles, trust me, everything gets shattered. Ok, the engine block wouldn't shatter, but everything else apart from that would. That means the car IS every tiny piece of plastic or glass on the road.
I'm of the opinion that these things take as long as they take. Every RTC is different so saying that it "shouldn't take as long as it does" is a silly argument, because you can't compare one RTC to another. All of your arguments are coming from a "driver caught in the queue on the motorway" point of view, but have you heard any arguments from people that are actually on scene? I mean they're not going to close a whole motorway if they don't have to, as it costs the economy around £1 million an hour to close a single motorway (iirc). The decisions to close motorways come from high up, not from a lowly traffic cop on the ground - he simply relays the situation to superiors who decide what to do.
.