It's mail-order FOMO.
You make a limited run. You include chase items ( 1 of X), variant items, exclusive items, short-packed items, Convention exclusives, website exclusives, in-store exclusives- Funko does that shit all the time... They're like Pokemon "Gotta Catch 'Em All". People mentally don't like holes in their collections. Collect All or Collect None. They do that shit with action figures, comic books, CDs, DVD's, statues, video games- you name it.
I guess it makes you feel special because you have something that someone else doesn't...
Look at when they released the MTG HeroClix- it was a blind box thing, BUT there was only 1 of each of the "4 Horsemen of the Apocalypse" WORLD WIDE. Talk about an "Exclusive".
How do I know. I spent almost $100 bucks on the Mr. Bean Funko Pop variant with the turkey on his head. I mean, I already had ALL the others...