Which element of cryptocurrency do you think is tough to understand?

Most of the people are aware of cryptocurrency. They know every thing about it like how to select best coin, how to use it and how to done payments using cryptocurrency payment getaways but there are a lot of people, for whom crypto is not believable. They know nothing about it or may be have little knowledge about it. So for them what is the most difficult part to understand or why they are not getting into it ?