Did you know that the Jetsons are shown to be in the same universe as the Flintstones? The Flintstones shows many different animals, showing indaviduality, and most of which are sentient enough to talk. The Jetson's shows almost no animals save for Astro. They never shows the actual surface of the Earth, only showing floating cities, or structures built on giant towers in the sky. It implies that conditions on the surface of earth are unsuitable for human habitation, and the majority of the sentient creatures perished in the inhospitable conditions are down there.

well I never watched the show much, but I'm sure Jacob's comment there is more childhood ruining than the image