Gambling is not for everyone because people below 18 years is prohibited from gambling and anybody that cannot control his emotions and accept his losses shouldn't gamble, because gambling will take the little money that you have from you and if you arw not ready to sacrifice it, you shouldn't gamble to avoid emotional trauma. Gambling is a means of entertainment and should be used for that purpose.
Except for the age limit imposed by most countries laws, as you mentioned, anyone can gamble. The fact that a gambler cannot control his emotions or have so much money to throw away doesn't mean that he cannot gamble or he is prohibited from gambling. This is because there is currently no legislation prohibiting these groups of people from gambling.
In fact, it is difficult to identify a gambler who lacks emotional control, and with online gambling, a person can become a problematic gambler without even people around him realizes it until he becomes addicted to the point where his behavior bothers family and friends.