I didn't like the leash pre-children. It will get to a point where your child can walk and will refuse to be held because they want the independence of walking. That's when you do the leash, it gives them "freedom" without fighting them when they want to be put down and walk on their own. It's probably a 6-9 month period and as hard as it is to believe it's not the same as walking a dog. You also don't do it 100% of the time either.
I was a "no-leash" person earlier in life.
Pickup truck bed does well too.