The difficult to understand how it works. The shadiness of itself and its community. I think those are the mains questions
they dont need to understading blockchain tech's working, how mining working etc, bitcoin is really simple, you dont even need to upload your identity to create a wallet, all they have to do just scan the barcode or addy, send and receive then i think it's not serious problem, it's quite easy
What I think they question is the legitimacy of bitcoin plus add the lack of knowledge to the cryptocurrency. That's why I think it is. They are more intact to physical currency than the virtual