They don't know the symptoms well enough to make a clear clinical diagnosis. Or worse, there is interference by insurance companies, worries about reputation, and lately professional reprisal by litigation as in the New Jersey Complaint against John D.Bleiweiss - litigation based in each complaint on treatment despite negative tests. The standard text Gel Electrophoresis of Proteins, Michael J. Dunn, ed. There are over 80 strains of Bb. Epidemiology is lagging.
Direct observation is rumored to be nearly impossible.
Ability to culture the organism is rumored to be next to impossible. So, what about the tests. Let me offer for consideration an approach that is well founded in medical history - a clinical approach. The symptomology is so similar in many respects that where the reader sees Syphilis in this article the reader may choose to substitute the term Lyme disease. I have seen no reference denying conjugation of spirochetes as of yet, nor have I seen studies on the evolutionary patterns of the species.