1. Vets aren't expensive.
Digital X-rays, blood analysers, anaesthetic machines, a purpose-built clinic, qualified nurses and great receptionists don't come for free (and alas no government subsidies) so we just can't treat at mates rates.
2. Medicine is fraught with uncertainty.
Animals don't read textbooks; 'Normal' is defined by a bell curve; Cancer will do as it pleases. Treatments fail. Animals die. Vets cry (oh believe me we cry).
3. I can't hear you when I have my stethoscope in my ears