Well, megaliths are a little different than obelisks, a point I remember from this particular documentary. Mainly, obelisks will break easily due to the mass distribution, unless standing upright. But your point reminds me of something else: would ancient Brits really build something like Stonehenge just to use as some sort of calender, to know when to start planting crops? It seems there would be easier ways. But, who knows what they were thinking?
Someday the archaeologists from another civilization will be excavating and deliberating about our culture. And some of them will say, “These ‘Americans,’ as they called themselves—surely they did not build these massive hundred-story structures of glass and steel just to pursue commercial activities. They must have had some religious purpose.” Then they’ll write b.s. doctoral dissertations theorizing about the purposes of our skyscrapers and imagining our religions. Especially the sacred, mysterious rites of the religion called “football.” That’ll really perplex them.