Some people don't believe in crypto especially to those who are lack of knowledge about it. Some know it but their mind is closed and not interested. Because it comes in their mind crypto is scam and not true and they are full of doubts in it. They think its impossible to earn through internet and don't see evidence the physical fiat money. They are also afraid being lost. And some other factor that comes in their mind.
You are correct. Some people did not believe at cryptocurrency because they are lack of knowledge at the benefits and opportunities brought by cryptocurrency. It always comes in their mind that cryptocurrency is just a scam. Some people are afraid to invest because they don't have enough guts to invest at cryptocurrency. There mind was totally closed because they believed it's just a scam, and they believe it is high risk to invest at cryptocurrency. But if only they spend time and embrace cryptocurrency thru reasearch i think they will be one of us later.