srw
It's a bit more complicated than that...
From the dull-but-true department: it's not "slowing down to walking pace to get a good look", it's an inevitable consequence of a busy motorway. When you hear a crash your first, instinctive reaction is to slow down a little bit. Once the first people have slowed down a little bit, everyone immediately behind them slows down a little bit more - until traffic is slowed right down to walking pace. That ripple in the traffic persists until the traffic is light enough that people coming to the back of it don't have to slow down at all - which is likely to be several hours later in the case of a busy motorway like the M5.To the drivers on the southbound M5 last Friday morning, the ones that caused a miles-long tailback and added at least 15 minutes to my journey.
Yes, someone had an accident on the other carriageway. That does not mean you need to slow down to walking pace to get a good look. What were you going to do, stop to help? No, you just want to revel in someone else's misfortune, and by doing so create a situation on your side of the motorway that may well lead to another accident.
So, I'm afraid you shouldn't blame the drivers in front of you - you should blame everyone, including yourself, who chose to make the M5 busy. That, and the laws of physics and the training that all of receive to be prudent when driving.