You're not being brought up on criminal charges, you're being brought up on spiritual charges. Sins against God. Lawyers and 5th amendments do not apply. Lol. I think most confess their sin because they feel guilt. Tremendous guilt. We were taught from an early age that the only way to fix this and make it right is to come clean, confess our sin to the elders, and ask for jehovahs forgiveness. But serious sin, as you described above, such as fornication, could only be forgiven through the elder arrangement. We couldnt recieve forgiveness directly from god. So, as painful as it is, many who commit "serious sin" feel a strong urge to confess, there by incriminating themselves. When the sin is repetitively brought up at every meeting, multiple times, from the platform, it creates a great shame within you. And you're constantly admonished that the only true way to a clean conscience, repentance, and forgiveness, is to go to the elders and confess.
Crazy, I know.
Brainwash city.