1) I need 24x7 access to datacenters, some of which are in super sketchy parts of town (200 Paul, in HP) or are in the South Bay. A taxi might be an option, but a couple $200 taxi rides per month, plus an hour of waiting, would be a real pain.
2) I enjoy going on long trips, by land, with minimal planning. Rental cars are more cost effective with depreciation, but I like having a familiar car, very well maintained, and keeping my firearms/EMT kit/etc. pre-positioned in the vehicle. I'd consider flying, but my circle of equal pain makes driving to LA a 100%, and driving to vegas kind of borderline. I drive to Portland or Seattle even. Avoiding the hassle of the airport, more cargo capacity, and having a familiar vehicle on the other end, all add up.
3) Shooting sports. Going to a shooting range with a long-arm on public transit is a no-go :) Also, try taking 50 pounds of ammo on the bus.
4) Grocery shopping and other routine chores -- zipcar could accomplish a lot of this (and I have zipcared a pickup truck a few times, although their maintenance leaves a lot to be desired)
5) I love cars and driving, although not so much in SF itself. Parking in SF largely makes driving in SF unpleasant.
6) I enjoy having more stuff with me than I can comfortably carry, and the car serves as a portable locker. Having a spare laptop battery, paper, cases of bottled water, etc. a quick trip to the car away is nice. Plus, while it's slightly paranoid, having a vehicle with emergency supplies nearby, and a means of travel, radio, power source, etc. is reassuring -- if there were an earthquake or other disaster, there's a limit to what survival supplies I might have on my person, but my car is good for 96h.
If I were commuting between SFO and SEA a lot, I'd probably buy a second car and keep one on each end, just to avoid needing public transit. (and someday I'd go for a plane!)
None of this would be solved by a plush seat (like 1st class) or lack of crazy people and urine smell (like cabs vs. muni). I am probably an outlier in the combination of these, but not on each individual point.
I do try to avoid needing a long daily commute, either through wfh or living near the office, so I can keep the car parked and walk to/from the office. Still, I'd prefer a 10 minute drive to a 60-90 minute muni/bart/caltrain adventure to get to/from the office!