If you press the overflow button on the card, you can tell it you ride transit. If your transit system integrates with Google Maps, it will show that instead.
So every search engine gives me links to buy a ticket or check a flight, when I search for keywords about aeronautics. Want to find a motherboard spec sheet? Get 100 links to where to buy motherboards. And guess what I see when I search for mathematical models?
I had to ride a shuttle between campus and an offsite parking lot for about 8 months while construction was going on at work. The shuttle actually drove a couple of miles past where it'd make sense to head toward my apartment and then I'd have to loop back around in a pretty non-obvious way when I got to my car.
Google Now figured this out within a couple of weeks of when I started riding the shuttle and would show my route accordingly. I was actually kind of shocked it managed that without any active input on my end.
Short version being, it does seem be be a matter of development focus if the by-car side of things is that good.
This is very city and country-dependent. In Europe, car commuters aren't an overwhelming majority. The figure for the UK is 57% commuting by car.