The problem with the Rettungsgasse is that you only need one idiot to screw it up, but you often get many.
When I enter a traffic jam, I see most cars building it properly, but then I see one or two cars ignoring all others. I can understand that people might forget about it right when they arrive at the traffic jam, but once everybody arounds you do it, some just don't seem to get what's going on.
In other countries, like Austria, the Rettungsgasse is formed on the rightmost lanes, while in Germany, its on the left most lanes. Disparity of rules across EU countries doesn't help here either.
Also, for some reason, once the first police car goes through the Rettungsgasse, I often see many cars that just stop building it. Like "good job everybody, the police went through, we don't need the Rettungsgasse anymore!" even though there is still a jam. The ambulance comes 1-2 minutes later, and it has to fight its way through because of all these idiots.
In Germany the problem with the idiots is particularly bad, because while there are a lot of German idiots on the road, you also get a lot of international traffic with their international idiots on the Autobahn. If you learned to drive in a different country, chances are that you haven't even heard about this, and learning about all the different traffic rules of all the countries you drive through is a PITA.