It's not some super club or anything like that. Many teenagers make the decision to wait because they believe that to be what is best for them. For some, they choose to get a ring. People who are married wear wedding rings for many different reasons. For some, it is a reminder to them. For others, it a symbol of love. Others still wear the ring to show the world that they have someone who loves them. Not dissimilar, many teens who choose to get a purity ring have their own reasons for choosing. Some use it to remind them of their commitment to God and themselves. Others wear it to make it known to others out there that they are not interested in the type of relationship that will involve premarital sex and that if the other person is, it is a waste of time to pursue the ring-wearer. Others wear it as a commitment to their future spouse and wear it sort of like a place-holder until their spouse gives them a ring. Then, they can present the ring to their spouse as a symbol that the wearer had been thinking and praying about their future spouse, as well as preparing and guarding their heart for their future spouse.
Many people who make the abstinence commitment do not choose to wear a ring and that's okay, too. It doesn't make their commitment to chastity any less valid or important. Others still make no commitment. That doesn't make them any less marriage material (or any thing else) than those who did wait. The ring is solely for the wearer and has a special meaning for him or her. Many people with rings marry people without rings. Many people who abstained and didn't have rings married people who abstained and wore rings. People who abstained and wore rings married people who didn't abstain. In my specific situation, my husband didn't have a ring for me. It didn't matter to me that he didn't have one to give me, but he has told me how much he values the ring that I gave him.
But, again, the choose to abstain is a very personal one, as is the decision to wear or not wear a ring. Abstaining or not abstaining as well as wearing or not wearing a ring does not make any person better than anyone else. All it means is that you have made a commitment to something and might choose to show that commitment in a piece of metal worn around a finger.