I think one of the most important reasons why these companies never put ads on television is that they occupy the most of the market share in that area, almost monopolized in its most cutting-edge technology development that not many other companies could afford to keep up with. Just like Boeing and Airbus, they are the most known airplane manufacturers in the world, both are confident to have customers that keep coming in no matter whether they put ads or not. However, there are possible other reasons for their silence on the TV marketing, including that customers cannot being usual households, that the product cost per se is already astronomical, etc. In general, those companies who are not interested into marketing on TV may not intend to attract the population that watch TV in the first place.