Taking Toddlers for a walk

I really don't know what's wrong with a leash on a toddler, like how is a stroller any better? Kids like to be out and explore and getting exercise not sitting in a stroller (which serves a purpose too but don't get why ppl think it's better than a leash). And sure you can hold a kids hand but what if you have 3 kids or your kids prefer to have their hands free? I mean the toddlers I have seen have had no issues with it and as long as the kids are happy and safe it seems like a good thing to me