Why .doc files are still around
Government archives, legal departments, academic institutions with 1990s document libraries, regulated industries that froze their templates twenty years ago. The format was retired by Microsoft in 2007, but billions of files exist and they don't all migrate. If you're trying to feed historical content to AI or build a searchable knowledge base, you'll hit .doc files.
What's lost vs preserved
Preserved: paragraph styles, headings, lists, basic tables, bold/italic, hyperlinks, footnotes. Best-effort: complex nested tables (the binary format encodes them differently than .docx), embedded equations from old Equation Editor (rendered as text approximations), WordArt (becomes plain text). Lost: macros (intentionally — security risk), custom XML tags (the binary format predates them), some legacy field codes that have no modern equivalent.