Time is money - Using mass transit takes on average 1.4–2.6 times longer than driving a car.

I have wondered about this in the past but never actually researched it.  Mass transit works in a few cities but is woefully underutilized and extraordinarily expensive in most cities in the US, primarily due to the  geographical expansiveness and low density of most American cities.  

Mass transit is hardly used at all by the Mandarin Class outside of Chicago, Boston, New York, and a small handful of countries.  

Other arguments attempting to explain why Americans don't use mass transit are more polemical - Americans are racist and don't want to mix on buses/trains, Americans are classists and don't want to mix on buses/trains,  Americans are too fastidious about cleanliness, etc.  At the far fringe these explanations might have some small predictive power but can pretty clearly be dismissed as marginal.

The most obvious explanation of all gets acknowledged but is rarely discussed or explored.  Time cost.  My experience in Stockholm, Sweden; Sydney, Australia, Atlanta, Georgia, and half a dozen other cities has been that mass transit takes a lot longer to reach a destination and is necessarily inflexible (i.e. transit schedules).  There are a few cities where this is not true, typically very dense cities.  

Time cost of using mass transit is real, but how much is it?  That is what I wanted to know and have never seen estimated.  From Disparities in travel times between car and transit: Spatiotemporal patterns in cities by Yuan Liao, et al.  From the Abstract:

Cities worldwide are pursuing policies to reduce car use and prioritise public transit (PT) as a means to tackle congestion, air pollution, and greenhouse gas emissions. The increase of PT ridership is constrained by many aspects; among them, travel time and the built environment are considered the most critical factors in the choice of travel mode. We propose a data fusion framework including real-time traffic data, transit data, and travel demand estimated using Twitter data to compare the travel time by car and PT in four cities (São Paulo, Brazil; Stockholm, Sweden; Sydney, Australia; and Amsterdam, the Netherlands) at high spatial and temporal resolutions. We use real-world data to make realistic estimates of travel time by car and by PT and compare their performance by time of day and by travel distance across cities. Our results suggest that using PT takes on average 1.4–2.6 times longer than driving a car. The share of area where travel time favours PT over car use is very small: 0.62% (0.65%), 0.44% (0.48%), 1.10% (1.22%) and 1.16% (1.19%) for the daily average (and during peak hours) for São Paulo, Sydney, Stockholm, and Amsterdam, respectively. The travel time disparity, as quantified by the travel time ratio 𝑅 (PT travel time divided by the car travel time), varies widely during an average weekday, by location and time of day. A systematic comparison between these two modes shows that the average travel time disparity is surprisingly similar across cities: 𝑅<1 for travel distances less than 3 km, then increases rapidly but quickly stabilises at around 2. This study contributes to providing a more realistic performance evaluation that helps future studies further explore what city characteristics as well as urban and transport policies make public transport more attractive, and to create a more sustainable future for cities.

Lots to be argued about in terms of methodology, etc. but it is a stake in the ground.  Four cities (Sydney, Stockholm, Sao Paulo and Amsterdam) - "Our results suggest that using PT takes on average 1.4–2.6 times longer than driving a car."

If you are a lawyer billing out at $300 an hour, the excess cost of using mass transit versus a car is between $180 and $480.  In a developed economy where productivity is high and where services sector is a large portion of the economy, the time cost of using mass transit is prohibitive.    

It explains why white collar users tend to be few and far between (cost, not classism).  It explains why ridership is low (too expensive compared to the alternative).  

Some cities, the equations work such as New York and Boston but most places?  The numbers don't work.