Veneers are only used for aesthetic reasons. They are made out of porcelain, which is a very esthetic material. It is usually used to correct for any shade/shape/crowding/spacing issues that the patients may have. They require minimal preparation, and can usually be done without using local anesthetic.
Enamel micro abrasion, crowns and veneers are considered less conservative, however, they have their indications based on the esthetic concerns of the patient