There are a few reasons.
Your parents are trying to protect you. That said, the older generation are not as well versed in modern ways as we are. To a flaw, your parents will always think they know better, and while most of the time this is true, they do not see the times when they do not.
Imagine a 10 year old coming to you, and explaining that you should put all your money into sand because that's the new big thing. It's understandable to be weary of something you don't know, and try protect your loved ones
Try explain it in a way they can understand and show proof, logic and risk vs reward in numbers.
Yeah and additionally, they're just protecting you from any cybercrimes that could make your life risky. The fact that they knew that you're making money, it makes it questionable for them how you could earn that money and start asking themselves if it is legal and real one. It makes them think that how in the world can you earn money in just sitting and typing at thw screen while they're spending their time working and traveling to their company just to earn