Jim Macklin wrote:

You can fly under IFR rules in uncontrolled airspace Class
G.

Well, yes, technically you can but what do you do for an instrument
approach when you cannot leave the en route altitude under 91.177?

And, in any case, the airlines cannot fly IFR in Class G airspace except
when conducting weather avoidance. And, since most of them are above
14,500 these days that provision is mostly moot.