I should imagine it has a lot to do with the reliability of tests. Also, with the dangerously dubious tagline that Lyme is hard to get, easy to cure.
If people were aware of the true nature and degree of risk associated with any TBD, certainly with Lyme, maybe regular testing would become more of a routine. Then - maybe - the outcry against the inadequacy of current testing technologies and schemes, e.g. the CDC's 2T mechanism, would ratchet up in intensity.
As to whether there were any reasons for doctors to consider a Lyme diagnosis - I don't recall. But I will tell you this: If I had a patient in a Lyme endemic area...or in any area that was known to be a habitat of ticks, Lyme would frequently be on my list of differential diagnoses if any of the common symptoms presented.
Unfortunately, many believe "the usual tests" do far less than "fine".
Hence the effort to develop better tests...