A while back, people would start at lower temperatures, then step up to the final mash temperature. It was harder to get the starches out of the grain and enzyme levels were lower. Single step infusion was relatively rare. But with modern fully-converted malts, it's used most of the time.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk