I'm sure the answer is neurochemical in origin, and I'll probably never know it. In the meantime, these are remarkably good. I used Maida Heatter's recipes for cake and frosting, deviating from them only to decrease the sugar in the cake by half a cup, and whip the frosting in my mixer to make it airy. I also dug up my giant icing tip and it does make for a pretty and easy cupcake top.
Why are cupcakes suddenly the thing? I'll bet money there is a single PR agency somewhere responsible for the craze.