I wouldn't know about that -- I haven't carried or horded much cash in over 5 years now.
Cash is uninsured for loss, everything I receive is by check, wire or ACH these days.
Where do you get all of your cash? Take it out of the bank and hide it in the house or bury it in a tin can? If you horde gold in you house it is uninsured unless you buy a rider on your property insurance -- same for jewelry. You are more likely to have a break-in than have a bank holiday. The government taxes your cash assets with inflation anyway. Most of the time cash is a lousy investment.
IDK about debit card vending machine security. The premise is fine but it looks like an easy opportunity to place a card skimmer. I carry a RFID secure wallet as magstripe credit cards are not that secure. I have a prepaid card but the $3/mo service fee is expensive for the little I keep on that -- good for a vending machine or some other untrustworthy location or use

Porn test buys

can only get carded for the $40 or $60 on that card.