Funko POP! Figures: Why so limited?

[Stardust Live 43]

Funko pretty much makes a POP! out of everything and anything they can get their hands on and are sure will sell (and even some stuff that ... kinda would never sell). With the MLP line, it was only a few ponies that got the Funko treatment. Some I understand (Twilight, Pinkie, Fluttershy), but some I don't (Celestia, Spitfire). Why weren't the Mane Six completed? Why was Celestia picked for POP! treatment? Why wasn't Luna added, or Cadance considering the Royal Wedding? Why not other fan favourites, like Lyra and Bon-Bon?

I'm honestly confused as to why Rarity and Applejack were left out. Any ideas? I would have LOVED a Luna and Cadance POP!

 

(I know about the vinyl figures, I am talking about POP!s specifically)

[Octavia Heartstrings 28,397]

Because completing the Mane 6 and the Princesses, and adding more fan favorites, would make far too much sense. 

[Cagey 4,205]

Wow, I didn’t even know which figures are and aren’t a thing. Weird. 

[ShadOBabe 18,984]

Well Celestia is best pony, so that makes perfect sense to me. 

But yeah the Mane 6 should have been completed. On the other hand, Applejack and Rarity are CONSTANTLY left out of merch, so I'm not shocked. Which sucks because I love them the most out of the lead characters.