Syphilis is still treated by drug-of-choice good ol' penicillin. There are more choices than just that. I believe it's eaily treated, although people may ignore the possibility they might have it.
Lyme disease is dead simple to treat in the early staged. Again, people may want to believe they're "just fine". I knew someone who ended up with tertiary Lyme, because he just didn't seek treatment when the rashes appeared.