Easy. For most people, BTC IS a scam, in that it has no apparent advantage over fiat.
Some people do indeed think Bitcoin is a ponzi scheme or something similar to that, but it's just a small group of people. They only talk and think like that because of the media that has been hammering on Bitcoin like it is an insect that need to be squashed. It's a shame that people don't look in Bitcoin themselves to find out the truth.
The media is making a lot materias about bitcoin darkeness business, ilegal activities, and for sure the biggest ponzi ever created. Soo several people believe in everything they see, being real or not they believe, on this time bitcoin growing slowly because those news, if the news stop attack bitcoin, it would be traded at several places.
That's so true. I have only heard of bitcoins in the mass media that involves crimes, especially theft and money laundering. Those are the common news about bitcoins now a days. Still, only very few people may start hating based on those type of news. For others, it serves as promotion of bitcoins to spread out.