Why is it that the other cults get so much more air time than the JWs
In the particular case of Dianetics/Scientology, it is because they deliberately seek it out. The Church of Scientology ran paid ads and has their high-profile celebrity converts on the talk show circuit speak up about being Scientologists. Celebrity Witnesses are encouraged to be humble (to some extent, at least); recall the reports that Prince wore disguises when going out in field service.
Compare the number of Average Joe Citizens who know that Travolta, Cruise, Alley, etc. are Scientologists to the number who know that Prince, Michael Jackson, and the Williams sisters were/are Witnesses. Prince was a member of WTBTS, while Cruise is a spokesman for Scientology.
Another possibility is that compared to Scientology, Unification Church, FLDS, Westboro Baptist, Jonestown, Branch Davidians, Heaven's gate, etc. the Witnesses just don't produce many juicy headlines for the tabloid news. Frankly, they are rather boring to outsiders.