Excuse my ignorance, but why would it even be forbidden for people to pump their own fuel? I live in Florida, and I have never even seen a fuel station that isn't self service. I thought full service stations ended years ago..
Well, Oregon and New Jersey are the only two states in the United States that have it written into their state law that motor-vehicle operators are not allow to pump their own gasoline at the "typical" fuel stations (e.g. Shell, Chevron, Exxon, 76, etc.) One reason they don't allow people to pump their own gasoline is they are afraid people are going to start fires from static discharge when they touch the pump handle. However, 48 other states don't seem to be having much of an issue with this...
So, I don't really know what other reasons they have. As FordGuy100 mentioned, you are allowed to pump gasoline at card-lock stations. Typically (in Oregon anyways) card-lock stations are used by loggers, emergency services, trucking companies, etc. Most regular citizens do not use these, as it requires getting a special card to be able to pump fuel and you pay a monthly bill. But, as the OP stated residents in Oregon are allowed to pump their own diesel, because it is not consider a Class 1 flammable liquid (i.e. it is not the easiest liquid to ignite). So the likelyhood that someone will cause a fire while pumping diesel is a lot less than someone pumping gasoline.
As FordGuy100 said....it is pretty nice on the days that it is just flat ******' rain to stay inside your rig and have someone else fill it up. But, I haven't melted in the rain yet.....so I guess it isn't that much of an excuse!