Well to think of it, even outside crypto it happens.
Those fake giveaways where you do entries in a certain site and would like you to share their page, join their discord, or follow them in Twitter. Most of those just ended up being nothing and I have never heard someone yet that they got this certain item from a giveaway by just sharing or boosting their audience.
It also happens in Youtube, now that many Youtubers are just hungry for revenue, but they don't care about their audience at all.