I'm not sure it's really helpful to compare dog ownership to car travel.
Cars are useful, for a start - as are some dogs, and of course dogs are valid. But risks are inherent with travelling at speed which is, apparently a vital part of modern life. That's why these risks are accepted and everything is normally done (by good, responsible drivers) to avoid them.
Dogs ought to be as safely kept as possible, yes if you have a dog that's unlikely to injure or scare people then by all means don't use a lead.
If you have a playful, stupid, (in the nicest way!) or volatile dog, keep it on a lead unless there's no one around for it to attack.
It's just common sense isn't it? I always try to maintain a level head around dogs, if they look cross or sound very loud, or if their owner is acting badly/aggressively toward them I will cross the street and keep my kids close.
If it's a normal person with a sensible looking dog I will give the benefit of the doubt.
Sadly we were approached by a very playful dog on the beach one day when ds1 was about 2yo. It was a retriever I think or a lab, not sure, don't know much about dogs - anyway, soppy, harmless looking dog.
Before I could do anything it ran at ds, jumped up on him, on top of him, knocking him flying with no warning. As I helped ds up (who was very cared and upset) the owner approached and laughing, said that we were lucky, because the dog had broken someone's ankle last week.
ds was then terrified of ANY dog for about 3 years. I didn't encourage this, I did layman's CBT with him to try to retrain him into not being terrified.
It was hard work. I don''t think it was fair or justifiable tbh. That dog ought to have been kept to heel or on a lead. It was a busy area.