>>19759993My guess is it has a lot of nostalgia value.
Back in GSC when it first appeared it was only found in Dark Cave, and it was really rare.
It'd be extremely unusual to find one in those first two or three minutes in Dark Cave when starting the game, so you'd most likely find one when you enter the cave from the opposite side after finishing the last gym, right after going through the whole region, thinking you've seen it all.
Then, after dozens of Zubats and Geodudes, when you're not really expecting anything new WOOSH.
"Holy shit what's that??".
So you find yourself facing something that's really fucking bizarre and looks really out of place, yet at the same time it looks kinda cute and probably inoffensive but it looks so weird you don't really know what to expect. It was such a unique encounter, and you felt like you had to catch it if only just for the sake of having it.
I don't know, maybe it's just me but after 13 years I still have that memory crystal clear in my head.
It's kind of similar to how Pikachu got so popular in the first place: a Pokemon that's kind of rare but not that hard to find that you won't just stumble upon one, found in a regular route where you least expect it, with a design that stands out from what you expect from that place so that it immediately catches your interest.
