The record doesn't get dropped, per se. Absent being on the sex offender registry, or having been transferred to adult court, the record is confidential. However, some agencies are entitled to the records anyways.
If you need a security clearance for a civilian job, that record will be available. Likewise, if joining the military, you MUST disclose your juvenile record to your recruiter, or you run the risk of being discharged as a fraudulent enlistee.
Additionally, we're seeing an increase in the use of juvenile records for sentencing enhancements as an adult.