I do somewhat agree with what you're saying, but actually none of your points are specific to bitcoin. You could make all the exact same arguments you just did for dollars too. Maybe not the physical paper kind, but credit card numbers, bank account numbers etc etc. As for physical paper, there's nothing stopping you printing out your bitcoin wallet key and keeping that securely instead of in computer memory.
A failing in computer security and failing to make backups all amounts to the same potential for loss no matter what the actual form of the money stored on or accessed by the computer is, so citing computer security is not actually a reasonable justification specifically against the use of cryptocurrency (such as bitcoin) vs conventional currency because it is a separate issue that can affect both.