The Jetsons and the Flintstones are essentially the same show, each involving a family with contemporary culture, values, and problems, one taking place in a futuristic setting and the other in a prehistoric one. As the show's were produced by the same company they were able to crossover in a 1970's made for TV movie. When the two families encounter one another they find that they share a common language, morphology, and culture. They have similar phraseology, are able to fit into each other's clothing, and even listen to similar music. An average viewer might reasonably believe that this means that the Flintstones are living in the past and the Jetsons in the future, but wouldn't the striking number of similarities instead indicate that the two families are, in fact, living in the same time period? What if instead of a time machine, the families were instead just using some kind of teleportation device that was transporting them from the Earth's surface to the Jetsons home high above the sky? What if the Flintstones are part of an almost slave labor sub-class who is forced to live in substandard conditions to support the frivolous lifestyle of the upper class living in the sky above them?
So many quirks of both shows begin to make sense under this explanation. For example, The Jetsons offers the viewer no explanation as to why "everyone" has chosen to live in apartment buildings in the sky, and the viewer never sees what is going on under the cloud cover below the family's apartment building. (A passing reference in the Jetsons movie seems to indicate that this is due to pollution, as the buildings are shown rising above a thick layer of smog. This may help explain the "prehistoric" setting of the Flintstones, which is a world ravaged by the pollution created by the upper class living in the sky.)
This explanation also explains where the material to make Sprockets comes from. How would a society who lives entirely in the sky mine the minerals necessary to make sprockets? The explanation is quite simple. The minerals are coming from the Earth's surface, where Fred Flintstone tirelessly mines day after day after day.
But what is subversive about the Flintstones is that, even though they are clearly the exploited underclass being taken advantage of by a cruel upper class, they are a generally happy people. They are amazingly poor and unable to afford the many luxuries the upper class living in the sky has, like robot maids or flying cars, and yet they never wallow in self pity about their economic situation. Instead, the show displays them thriving and enjoying their station in life, as if they were completely content being members of the poorest working class. To them, the gross income inequality present in the world, where some live in futuristic splendor while others literally sleep on rocks, really doesn't seem like a big deal. Sure, they may not enjoy as high of a quality of living and their education system is clearly lacking (as is evidenced by Fred and Barney's numerous idiotic schemes), but the show brushes all of these issues under the rug, as if to say, "look being poor isn't so bad."
Further supporting the animators argument that gross income inequality isn't really such a big deal, they frequently show that life in the upper class isn't all it's cracked up to be. While Fred Flintstone is generally jolly, George Jetson is a cranky little man who never seems quite happy with the numerous luxuries being born into the upper class has afforded him. The rich in the Jetsons/Flintstones universe suffer just as many, if not more, problems than the poor living below them. In this way, the shows seem to be arguing that being poor isn't really that big a deal. By displaying George's constant problems and annoyances, the creators are saying, "look being rich isn't that great anyway," while all the while Fred and his family merrily trot along through their lower class existence.
Or maybe I'm just reading too much into it ....