Science fiction, particularly space operas, can be dismissive of doctors. Most of the time the "doctor" is just a diagnostic machine that gives miracle meds and maybe 3d prints new body parts.

Maybe it's prophetic: authors saw the writing on the wall and decided a doctor is a glorified mechanic who works on the most boring machine around (which hasn't changed in 100k years). Or maybe authors just decide the space was better filled by an ex-space-ninja or similar.