To me, the main reason is because people are being scammed using bitcoin, so people then choose to hate it and then called it scam mostly out of the frustrating it brought them. I'm talking about people who are scammed in the name of investing in bitcoin. Another reason could be the blackmailers; those who don't want bitcoin to be globally adopted so they accuse bitcoin to be scam hoping that people don't choose to use it and will misunderstand it's use.
Bitcoin community should be aware about this especially those who are newbies that is the main victim of scams.
They are getting scammed because they think that bitcoin is easily achieved and stored. They think that if someone tells them that there is a bitcoin giveaway, they will immediately react to that and become their victim. Also, people are really easily attracted in easy money and bitcoin is not like that.
This is a major reason why I advise we stop looking at bitcoin as an investment, and start looking at it as a currency. It's mostly in the name of "investment" that people get scammed.
