At the core this behavior is simply a version of social proof. Parents see what other parents do and/or kids see friends being picked up and then put pressure o

At the core this behavior is simply a version of social proof. Parents see what other parents do and/or kids see friends being picked up and then put pressure on their parents to do the same. Then it gets to a tipping point where it just becomes the thing that you do (and nobody thinks otherwise or wants to tell their kids they won't do this or questions it). It's also a way for a parent to think somehow they are doing the right thing and get a little enjoyment in their head (despite the time involved or wasted) 'I am a good parent'. Doesn't involve as much effort as other things a parent does (or should do) it's simple (other than the time).