The wrinkling of the glans is called keratizing, and all circumcised penises get that. Its caused by the glans being exposed to the air constantly and rubbing against clothing. Its a process where the skin of the glans gets thicker and tougher, and in the process, less sensitive. When the glans dries out, it tends to form wrinkles or crevaces. The glans is really designed to be covered by the foreskin, and kept moist at all times. Think of the glans as similar to the inside of your mouth cheek, where the skin inside your mouth is constantly kept moist by saliva. If you dried out the inside of your mouth, the skin inside it would change texture. Same thing with the glans when the foreskin is removed. For what its worth, I'm circumcised and my glans is wrinkled too - mostly noticeable while flaccid, but less noticeable when hard.