It is that much harder to pull a person out of a luxury car and put them onto transit. Soccer mom technologists have the most complex transit needs of any group in the corridor. Waiting time where the commuter is not progressing towards destination seems psychologically 3X slower than regular time. Service reliability is not such that commuter can transfer without worry of delay - this is a stress inducer. Must be able to come and go at will.
Some cars serve as security blankets.
Their trunks contain many important items that are unpredictably needed. It is inconvenient or impossible to carry all of these items around on transit. Note that objections like these typically do not come out of statistical transit surveys, but may actually touch closer to the heart of psychological resistance to transit. The separation from the rest of the world provided by the car cabin is a little cocoon of sanity. Reception while taking transit is worse than by car.