Because usually the argument is about saving lives, and cars kill far far far far more people then guns do. Cars are also used more for crimes then even guns.
That's not even close to true. US traffic fatalities and US gun deaths are about equal each year at around ~32,000 people.
Its not an argument I would make, but its logical if you start off of the presupposition that we need to save lives.
It's not really logical at all, because even if cars killed more people than guns do (and they don't), that argument would only make sense if protecting lives was literally the only thing that mattered. Cars have vastly more economic and social utility than guns do. Ask the average person in the US what they could more easily do without, their car or their gun. The vast majority would say their car is more important.