Until a split second later they remember how convenient cars are, and how lazy the thinker is.
Depends, innit. Travelling from my village to the town centre , they're massively inconvenient (unless you're infirm, or need to carry a lot of stuff) because the volume of people who think they are convenient chokes the roads after about 7:30am on weekdays, and 9-10am on weekends. Add to that the fact that you need to leave the things somewhere for a lot of the day, and only the UK's inherent cultural bias towards the car makes them seem like a better option than walking (slower, but no need for parking or sitting in the traffic) or cycling (usually quicker, dedicated bike path available for 2/3s of the journey, may have the parking issue though).
Ideally, people would use different transport modes where they are best suited, but the evidence (both from where I live now, and back when I lived in Heald Green) suggests that an awful lot of people use a car to do everything, pretty much.