Not a resident but my partner is from SG. One of the reasons I often hear is that families(mom, dad, kids, grandparents) like to travel together, and the elderly are not always mobile enough for public transport. Public transport is really fantastic, but it doesn’t cover every single need.
And of course it’s a status symbol, some feel the need to show they’ve got the wealth to own a car.
Again, I hear these things second hand and am colored by my partner’s beliefs :) Maybe a SG resident has a better (or different) explanation. edit:
In my eagerness to share, I realize this doesn’t really answer your question. Sorry about that :)