It's because that in the original trilogy, the Force was built up as a magical, mysterious source of power and not something gained by a symbiotic exchange from blood parasites.
If the Force was set up as something gained by a symbiotic exchange from blood parasites, then people would be fine with Midi-chlorians.
EDIT: I don't give a flying fuck that I'm apparently '10 years late' or so.
10 years ago I was 5. And 5 years ago, I was 10. So I didn't fucking care at the time, nor was I into computers as I am now.
If the Force was set up as something gained by a symbiotic exchange from blood parasites, then people would be fine with Midi-chlorians.
EDIT: I don't give a flying fuck that I'm apparently '10 years late' or so.
10 years ago I was 5. And 5 years ago, I was 10. So I didn't fucking care at the time, nor was I into computers as I am now.