what is it about the unattainable that makes it so attractive?

what is it about the unattainable that makes it so attractive?

let's take this on a basic level:

i want a candy bar.

right.

now.

i can almost taste the peanut buttery chocolate-ness of a Reese's.

But I'm 10 cents short of exact change to get one in the vending machine at work. So, no-go on the candy bar.

It's been 5 minutes. I want one so badly my fingers itch.

It's been 10 minutes. I have been considering trading sexual favors for said candy bar.

It's been 15 minutes. I may actually die of lack of candy bar.
I wonder if adding this to the autopsy report would authenticate it as a cause of death.

I want the candy bar not because i'm hungry, but because I can't have it.

I want the attention because I can't have it.

I want the 6 hours of solid sleep because I can't have it.

I want the 2.5 and the picket fence American Dream because I can't have it.

I want to play in the rain... oh... wait... we did that one this weekend
(see below)