When we are planning to invest our hard earned money we don't just take a haste decision. We explore the options, we seek advices from various people, read, search and explorer. Our parents can be a part of our journey and they can guide us. If we owe the money that we are going to invest from our parents in some way, they have a say in that matter and they are justified to dictate. But if it's your sole money, they can only be a third party giving us their suggestions.
Some cultures have more parental control even when children are grown up. And it comes with its own sets of pros and cons. My mom helped me a lot as a guide in initial years when I started investing and was clueless.