The A-file opens the first time the system touches you and never really closes — every petition, every officer's worksheet, every border note accretes. Adjudicators read it before they read anything you send today.
Because the government will. Filing anything substantial without knowing what the file already says is briefing blind: the inconsistency you did not know about beats the argument you did. The A-file review finds the landmines — and, as often, finds the forgotten filing that helps. The request guide covers getting it.
If you've filed almost anything with USCIS or been processed at consular/border stages, records exist — the numbering and location vary; the request finds them.
To the beginning — files from prior decades routinely surface, including paper nobody in your family remembers filing.
Records aren't purged on request, but demonstrable errors can be corrected and context added — and knowing what's there lets every future filing answer it.