Try handling two sets of twins under the age of two, solo.
If one of the eldest likes to bolt, you’ll need someway to control them.
i’ll be finding out if I will need these in 4 months after the second batch is out.
I didn’t see this a lot when my kids were little, maybe because we lived in a rural area and everyone knew everyone. In today’s world, as crazy as people are, in an amusement park or such, how fast kids can bolt, I’d absolutely do a leash!