A safe deposit box is at a bank, at which point, why not just put your money in the bank?
And fire-proof safes aren't "fire proof". They're generally rated for a reasonable amount of fire resistance - 1 to 2 hours - which is usually enough time for a house to burn down around them and be extinguished (they also only promise to protect paper, for example).
Whether they would survive the inferno of a bushfire, wherein the house is not extinguished, is far less clear.
And fire-proof safes aren't "fire proof". They're generally rated for a reasonable amount of fire resistance - 1 to 2 hours - which is usually enough time for a house to burn down around them and be extinguished (they also only promise to protect paper, for example).
Whether they would survive the inferno of a bushfire, wherein the house is not extinguished, is far less clear.