Warum? S01 E30 Why do product drops like Swatch, Lindt, and Apple cause buying frenzies?

Swatch, Lindt, Apple - companies constantly release limited editions, and these always result in enormous queues outside stores, sometimes even involving fights, as people try to get their hands on one of the coveted products. But why do people sometimes stand in line for days? How can such sales hype be explained?