Modern blue jeans are broken in by pre-washing denim with strong oxidizers (a hard-to-find consumer equivalent is RIT Fast Fade) for the "worn" look. Once sewn, jeans are scraped by hand at the knees, with other touches like rents and rips often added. The wrinkle lines you see at the crotch are called "whiskering," and special commercial molds are available to make the job of creating these easier.
Whiskers on jeans were supposedly trended by the world of hip-hop to draw focus to the crotch area. If you read a little further into whiskers, ask yourself, what type of animal has whiskers? an image-consulting blog asks. Adding a few lines to indicate use or long, proud "ownership" seems innocent enough, but this particular wear pattern would only come from years of working a desk job, or maybe if you were a cowhand who eternally lived in the saddle, in which case the creases would be dingy brown, not white.
Our thoughts are shaped in a stealthy way. It's not easy to find "clean jeans" these days, with no suggestive markings.