It initially started when the hobby was niche enough that groupbuys were pretty much the only way to get the factory time to do enough items to make it economical.

Nowadays it keeps happening because a) its a win for the designer/company, they get immediate payment with no risk of not selling their product if they just did it in stock b) there are still smaller designers who wouldn't be able to get their designs made without the GB model

I am hopeful that with GMK leadtimes being consistently insane, and now with KAT being blown up due to factory covid issues, that people will start to wisen up? But the FOMO in this hobby is real and its a fucking shame