Cash gifting

There seems to be a lot of those going around today. Especially on youtube. You see some person open up a fedex package that contains hundreds or thousands of dollars. How is this legal? I think this is just a pyramid scheme. Of course they all say it’s totall legal because you can get a certain amount of money from someone as a gift. They had these years ago and I know someone who lost 2k. I’m surpised these sort of operations haven’t gotten shut down yet.