The whole point is that there's a difference between saying that the popularity of a product can be caused by the lack of what would be a viable alternative (li

The whole point is that there's a difference between saying that the popularity of a product can be caused by the lack of what would be a viable alternative (like your example of public transportation versus cars), and saying that the popularity of one feature of a product is caused by the lack of alternatives that do not have that feature. The latter is more like saying "the popularity of 4-wheeled personal automobiles is caused by the lack of 3-wheeled personal automobiles on the market" or "the popularity of touchscreen smart phones is caused by the lack of smartphones with physical keyboards on the market."