It is becoming mainstream. Some people who originally got pierced for the punk shock effect are vexed to find that the bounds of acceptability have spread to embrace them. Piercings can be used for restraint. Some women lace their labia together. One I heard of had a zip fitted.
Men have other options.
You may have it done for your partner, but be sure you trust him or her. He went first. As soon as he was done, she laughed and walked out. While piercing almost always makes a sensual area more sensitive, the opposite can happen. One man's earlobe stopped being erogenous.