I know, this might not be the place to ask this but couldn't find another place to ask so...
I'm still kind of a small fry in this site and still learning its rules and mechanics but I still have no idea what these collectibles that everyone is obsessed about are good for? I'm talking about those items like feathers/candy/pinwheel/eggs...etc
*cough* I mean, they're just cute to most people. Quite a lot of people like trading this forum's currency for in-game things, because TBT bells are a bit more stable (and easier to earn for some) than in-game bells, considering you need to drop 10mil+ in-game bells for a lot of super popular villagers, e.g. Fang, Julian etc.
Also sometimes people have got what they want and need in their AC game, so they decide to trade some things for TBT items/ currency instead.
Collectibles are just kind fun to have and buy/trade... something else to spend forum bells on and another way to get involved in the community. For the more expensive/rare ones, some people will even trade 3DS game codes for them.
Also, to some people they seem to be a bit of a status indicator (not in a snobby way, just in general).
You don't really need the collectibles to trade, you can just use regular TBT. The collectibles are just useful for people who want things whose value in TBT might increase or who want to have something set aside for trading (since you can turn the collectibles into TBT but some people are looking for the collectibles).
Personally, I just buy the birthstones collectibles because I like the way they look on the sidebar. I don't care about the rest.
They're a very sophisticated device used by the mods which unintentionally created a huge demand for TBTB just little sprites that display under your posts. Just good for really...collecting, I guess. Oh, and profit. Feathers = profit. Rare collectibles = profit.