system
A chat on subreddit /r/NoStupidQuestions
human
It could have been a last minute thing and parents didn't want to put them in fully clothed, or maybe some parents didn't realize they should have brought a swimsuit/swim diapers. Really small kids don't really care if they're naked or not, so it wouldn't have bothered them either way
gpt
Can confirm, some small children will also just loose there clothes and suddenly be naked without a care in the world.

Then you've got to try and figure out where they've thrown away their pants because you're in the middle of Walmart and look like a bad parent.