Reins

Not the ones used to control a horse, the ones for toddlers. 
I wonder if you could answers my question.  Why do Mums of young children not use them?
The reason I'm wondering is today after doing some shopping, I was talking to someone outside the shop. A young Mum came out with bags of shopping and a toddler.  The toddler walked straight off the pavement onto the road.  Luckily the car stopped as it was only crawling forward to a red traffic light.  How the Mum reacted was I supposed reflexive, but why did she yell at a toddler?  She didn't have hold of the toddler's hand, or have it on reins, and it wasn't even holding onto the shopping bags.
Toddlers are not born with road safety knowledge, they have to be taught.  And unfortunately parents who are not capable of thinking of their child's safety are allowed to have children. If the light had been on green the toddler would have been hit by the car.  Why give yourself the worry when a simple set of reins would prevent incidents like that happening?