The Brown Scapular comes from the carmelite order and symbolizes their consecration to Mary. During the Middle Ages people wanted to be affiliated with these religious orders, the Scapular was given out by the Carmelites to lay people who formed confraternities. The Carmelites received the scapular from Mary in the form of an apparition.
Wearing the scapular is a sign of our devotion to Mary, and by completing the Little Office or if allowed by a priest substituting a Rosary we are placing ourselves in Mary’s protection.
This is from EWTN:
“In addition, the person has a special entrustment of themselves to Mary for their salvation. This, in fact, has been promised to those who faithfully wear the scapular: “Those who die wearing this scapular shall not suffer eternal fire.” This must not be understood superstitiously or magically, but in light of Catholic teaching that perseverance in faith, hope and love are required for salvation. The scapular is a powerful reminder of this Christian obligation and of Mary’s promise to help those consecrated to her obtain the grace of final perseverance.”
Essentially it is a sign that you are relying on Mary as your mother to obtain for you from Jesus the grace needed to persevere to salvation.
As far as I know, Catholics are NOT required to undertake the investiture of the scapular. In fact a Catholic should NOT wear and become invested in the brown scapular unless they plan to live appropriately, and fulfill what is required.
Simply if you don’t want to wear the scapular, you don’t have to, it is a devotion for some. If you aren’t comfortable with it, then don’t wear it.