The strongest reasons to "need" a labiaplasty are the presence of functional issues. These include, hygiene problems, rashes, chafing, bleeding, and difficulty wearing clothing. Problems with intercourse and dyspareunia (pain with intercourse) is also a primary reason to pursue labiaplasty. Labial tears during childbirth are another strong indication for a labiaplasty.
Otherwise, and in the majority of cases, a labiaplasty procedure (with or without a clitoral hoodectomy) is performed for cosmetic reasons. There is a wide range of "normal" appearing vulvar anatomy. More recently, with the increased incidence of nudity online, more and more women desire a "neat" appearance to the vulva. This is most commonly expressed as the inability to see the inner labia and clitoris while standing, with full outer labia (or labia majora). All of these aesthetic goals can be achieved with a thoughtful labiaplasty.
Find a plastic surgeon whom you feel comfortable with. I have turned many women down from labiaplasty surgery after providing reassurance and education on the range of "normal" but a consultation may help you to feel better about your appearance and address your concerns.