Is Coca Cola a Ponzi scheme? After all, they have to run ads to fool "suckers" into buying Coke as well.
No if Coca Cola was running a Pyramid Scheme/Bitcoin Scheme it would look like this:
Coca Cola makes a new invisible drink no one can see
Coca Cola rewards the first people who help create this invisible drink
Coca Cola uses payments made by new invisible drink consumers to pay the people who help created it
Coca Cola gets additional customers when the people who made the invisible drink tell their friends about it
Coca Cola pays customers to keep recruiting their friends
Coca Cola continues to sell these invisible drinks and gets everyone's money
Except, just because cryptocurrencies are numbers on a screen don't mean that they are non-existent. Just because cryptocurrencies are digital, doesn't mean that they don't exist at all. Numbers on a screen is pretty much how the entire world works nowadays.