Or it's a way to clear up a situation without incurring a life-altering debt and criminal record. We hear about the horrible stories, but people are generally people. If you're facing serious (felony) charges, actually guilty and they're building a case, don't know how to talk without spilling a bunch of possibly-incriminating details, think the cops have it personally out for you, etc, then of course shut the fuck up and assert the full extent of the process. But for many situations this can actually be terrible advice.
I was actually just on the other side of this with a juvenile first time offender (property crime). The kid was obviously guilty, open and shut evidence, and admitted it to the detective. The detective advocated for him (them), encouraging me to settle for a small informal cash restitution payment rather than insisting it go to trial. That kid has now been hopefully scared straight, without having a criminal record hanging over his head. I hope he can keep it that way.