Why do Arizona General Election mail-in ballot envelopes identify my Party?

[ThoughtCriminal]

On the OUTSIDE of the envelope for a GENERAL election, it identifies my party registration. It is visible to anyone that handles the ballots.

I understand how these ballots are handled AFTER they arrive at the recorder's office. But I feel that for a general election there should be NOTHING on the outside of the envelope that identifies the party preference of the voter. I don't understand why Arizona does this.

Another reason I take my ballot directly to our County Recorder's office.