Sorry if this has already been asked - but I'm curious as to why this has been retired?

I went through and collected all of them (totally my fault for not recognizing the big ol' RETIRED label) - just curious as to why since Morostide is going on.

Yeah, I was wondering the same thing (though I saw it before I went out to buy pumpkins, so at least I saved some sP, lol). Seems kind of odd.

Because only I can be the one true pumpkin king

...no but really I have no idea and I think it's stupid that it's retired because like, it's a one-tier achievement for having a complete collection, what harm is it doing? The new pumpkins every year are free