Because the county court and the DMV are separate tracks. The court closes the criminal matter; the DMV decides the driving privilege and states its own conditions, which commonly include proof of financial responsibility and a reinstatement fee.
More detail
The fix is procedural rather than legal. Get the DMV notice, read every condition, and work them one at a time. Where proof of financial responsibility is listed, that condition blocks the rest, because the state will not complete a reinstatement while it is waiting for a certificate. Two practical notes. First, a case disposed in county court can take time to post to the driving record, so a condition that looks unsatisfied may simply be in transit; the DMV can confirm. Second, if a court ordered something specific, a program or a fine, the documentation showing it was completed is worth keeping in hand rather than assuming it flowed through automatically.