Well in this case the age limit is based on most young people are still students and when they are at that age then it will greatly interfere with their growth and development process if they are familiar with gambling.
What you said is also true, even though someone has reached the age of maturity to do everything including gambling, it does not mean that they have an income, or they have an income but to fulfill their needs have not been fully resolved. I am of the mindset that one should have an income or at least be able to make ends meet before entering into gambling.
There are some students who are diligent and have started businesses to increase their pocket money, but most of them still ask their parents.
On the other hand, I think it's important to stress the need of teaching people how to gamble responsibly. Learning how to manage money and recognize the hazards of gambling are essential life skills. Everyone, regardless of age, employment status, or education level, will be able to make better decisions as a result
Student gambling is a serious concern, but it may also be a symptom of a broader societal crisis. Students aren't the only ones who could benefit from better financial education