What is the benefit or motivation for having Class G airspace? I'm looking at the differences between Class E and Class G (AIM 3-2-6) airspace in the United States and I get that there are different flight condition requirements depending on AGL/MSL altitudes, but if you're outside a Mode C veil and around an untowered airport (So you don't need a transponder, don't need a radio), why not make everything Class E?

I think the answer came to me while writing this out...is it this simple?

Does Class G exist because for whatever reason (Radar services not available, technical reasons, etc.) ATC is unable to provide IFR separation services in that area, so it has to be deemed "uncontrolled?"

Is there some other reason why Class G exists besides being a catch-all?


  Class G airspace (uncontrolled) is that portion of
  airspace that has not been designated as Class A,
  Class B, Class C, Class D, or Class E airspace.


Like is there some benefit that you get when you're in Class G instead of Class E? The only thing I could think of is that the flight visibility is less than 3 miles but more than 1, it's daytime and the cloud deck is lower than 500 feet AGL (since you just need to be clear of clouds and 1 SM visibility), you could take off VFR in Class G and you couldn't take off in Class E. (However, you'd still have to be sure not to be engaged in Careless or reckless operation (14 CFR § 91.13).)
You can also fly Ifr without a clearance in G. 

Remember that the entire purpose of airspace is to keep us from hitting airliners. It is not about keeping GA planes apart. When you look at wx mins that is clear. The FAA gives us the freedom to fly around in low vis so long as we stay out of the areas you'd find airliners. 

-Robert CFII