Many parents are too conservative to want to understand cryptocurrencies. They are used to living their own lives and deny everything new and incomprehensible. Probably the best way to let them know that the cryptocurrency market is a great place to earn money, show your profit, withdraw it to fiat. This way it will be clearer for them and they will understand that money can be earned without leaving home.
It's normal when our parents age is more than 50, i'm not blaming them for being denial because they don't even get the digital knowledge when they was young so they would not know digital assets could be worth so much in this current era.
The only way is let them think their own way and don't ask money to them if we want to invest on crypto but earn it by doing airdrops or bounty then the rewards allocate it for further investment.