And my personal investment in the crypto doesn't change because I introduce anyone to it. There's no direct bonus for me to bring them into Bitcoin.
Wrong.
Bitcoin has used signature campaigns, faucets, referral bonuses and more to directly reward each person that brings someone else in. This is the exact model used in Pyramid schemes. Each new sucker that buys bitcoin for a higher price than you paid, directly pads your ROI. So there is 100% a correlation between recruiting new investors and the rise in price of bitcoin
You fail to see the difference between advertisement and recruitment. Ponzi schemes rely only on referral bonuses (granted, used in the crypto environment as well) which means recruitment. But signature campaigns and airdrops are nothing other than you running ads for an organization. People who have ICOs in their signatures don't have to go around convincing people to invest in a certain ICO, it is enough that they promote the link by writing a comment, which serves as an ad.