Do people in Japan let groups of small kids wander around malls like that? People in the US can be overly paranoid sometimes, but I don't think I'd be ok with that for my kids.
[0]https://www.citylab.com/transportation/2015/09/why-are-littl...
But besides that that they'd do something stupid, or wander off, or something else along those lines.
I don't think this is just a US attitude, either - when we lived in Italy, we wouldn't have let our kids wander around the mall there, either, nor would other parents.