Why does holiday chocolate taste so much better?

It does not. That is just the placebo effect.

Have to disagree about the Reese’s Pumpkins. My favorite Reese’s peanut butter cups are the thins milk chocolate, more chocolate than the regular. The pumpkin ratio is just the opposite, the pumpkins are more peanut filling and less chocolate. If you haven’t tried the thins I highly recommend them. Here’s what the bag looks like: https://www.hersheyland.com/products/reeses-thins-milk-chocolate-peanut-butter-cups-3-1-oz-bag.html