Not sure that really helps. They are worried about their security because they don't want to get robbed. If I can break in and hold a gun to your head until you irreversibly transfer me all your bitcoins then you have basically the same security problem.
If your response is that they should keep all their bitcoins in a safe place then maybe we can think about what sorts of safe places you can keep items worth tens of thousands of dollars and then I think you basically end up back at banks.