Probably because you can't throw a rock without hitting one while surfing. Same reason people can't stand Zubat. And yet everyone seemingly likes Crobat. I never knew!
Even I got tired of Tentacool in Sapphire, since that game is nothing but surfing.
And it seems hard to keep conversations going in clubs, is something I've noticed, unless that Pokemon/character has enough material on its own to go off of. Say, a club on Gary would at least have a lot of source material to fall back on, and character dissections and what not. Pokemon are a species within a species... possibly within another species. Pokemon don't have complicated stories unless you give it to one, and even then, that story only applies to that one, not the whole.
That's the good and bad thing about the series. Pokemon by default are pretty bland save for some iffy things the Pokedex'll tell you, but at least you can take a few of them and make them much more interesting, and people can't really argue against it because it doesn't effect the entire subspecies. I still say it's the only franchise where everyone with active imaginations win.
Anyhow, that's why I fall back on "oh yes, I remember XYZ" or post found fan art, except I don't have any worth posting. No wait, lies. Found this yesterday (1st attach). The second picture's just because it's cute. Still, people in Japan don't draw enough of this family. -_-
ETA: After having looked at that second pic for a while, I feel like the series could use some more unassuming poison types. Like the aforementioned Tentacool. I tend to think water type before I think poison. Or the much earlier mentioned Bulbasaur. A cute little guy/gal that most people would instantly see as grass. I dunno if I'm the only one that sees the Nido family as something that just is. Maybe others make the poison association, but I'm so used to them at this point they're just rabbit chimera and nothing more. Heck, I forget they're poisonous until I see pictures of people holding one, and I think "isn't that dangerous?"
So yeah, more poison types like Tentacool, Bulbasaur, Oddish and Nidoran would be nice. I'm sure they can make some more charming critters that don't seem all that dangerous, like Horsea (who's 100% water, of course).