While parents might still provide financial support or have some level of influence, the 18-year-old is legally responsible for their own actions and decisions. They can enter contracts, vote, and are generally free to live their life independently.
Emancipation is typically granted to minors (under 18) in exceptional circumstances, such as abuse, neglect, or situations where the parents are unwilling or unable to care for them. Since an 18-year-old is already considered an adult, the process of emancipation is not relevant.