Not all financial scams are Ponzi schemes. Most are not. Ponzi schemes involve shady bookkeeping by the operator that conceals the source of fake profits.
If Bitcoin were an actual scam (and I don't think it is) it would be a pump-and-dump. Most ICOs were clearly pump-and-dumps.
There is a huge variety of financial scams, and it would be a fiscally safer world if more people knew about them.