The only person I have ever met who invested in physical gold (coins) on an ongoing basis was a survivalist who basically kept them under his bed with the aim of bartering them when the system broke down.
It is possible to invest in gold funds etc., but many people like to physically possess it.
Could Bitcoin overtake gold on this basis i.e. an asset you alone control without having to keep it under your bed?
No, bitcoin is great but if a person is holding gold to use as a currency in some kind of apocalyptic future, then it is logical to think that person believes that running water, electricity and the internet are not gong to be available, besides tell your friend that hoarding gold is an option but in that kind of future you will get a lot more if you are able to barter things people actually need, like medicines, alcohol, cigarettes and toilet paper.