Old people are not aware or don't have enough knowledge about the advanced technology that's why they also don't know the use of digital money. They choose to invest in gold and silver because it is a well known investment for decades already. They would choose to invest in a tested one.
I think that older people do not want to face greater risks and worries because the time of big nerves has passed 
My impression is that the people that hold these opinions lack knowledge, wisdom and experience. Old people invest (or don't invest) in gold and silver for the same reasons that young people invest (or don't invest) in gold and silver.
In the U.S., you don't find many people (both young and old) investing in gold and silver because they are simply not aware of it. I once brought some gold coins in to my work to show everyone, and most people had never held or even seen gold coins before, regardless of their ages.
In the U.S., gold coins were removed from circulation in 1933 and it was illegal to own gold bullion until 1975. The tradition of owning and using gold was destroyed in the U.S.
Because investing in gold and silver is not common, it is considered an alternative or unusual investments. Young people just getting into investing are not aware of gold and silver as an investment until they become more experienced (and thus older). If older people are more likely to invest in gold and silver, that is the reason.