Fear from hacking because if all of your money are now cashless it is prone to be hacked by someone and worrying this money will not return back to you.
We should fear a cashless world because the government can then now how much money we have and they would have to much control in my opinion. The balance in the world would not be fair at all.
There is a lot of hackers now, that's one of the disadvantage i see in cashless, because your money is not in your hand and you're still waiting when you recieve it. As long as you didn't touch your money you are not sure if you recieve it safe.
Yes a lot of hackers are here now and they are ready to take the money from bitcoin investors and hold it in their own wallets. Bitcoin is not easy to hack now because it is having a lot of other wallets and saving systems. If you are using offline wallets then it will be more beneficial and it will be hard for them to take your money. I dont know way people are afraid of lose and they want to use only one currency.