CPST here. If this is the US, if you see this (or something similar, or a completely unrestrained child) IRL on the road, call 911. If you just see it on social media, I’d call CPS. This is not just bad parenting, it’s actually illegal.
I have personally called 911 to report an unrestrained child and they took it very seriously. In my case it was a child in the bed of a pickup truck. A child in a high chair in a car is also unrestrained.
I also called the police on someone with kids in the bed of a pickup truck. They were on a busy 40 mph limit street, crossing an even busier 50 mph limit street. I didn't see if they caught the guy, but I'm sure he'll end up just telling his daughters to make sure they don't pop up and wave at other drivers at stoplights anymore.