In Illinois, it's illegal it keep children ages 6 and under in a vehicle unattended for more than 10 minutes. Someone 14 years or older must either accompany or be within eyesight of them.

These laws largely exist because of advocacy groups such as Kids 'n Cars[1] whose founders often had children who died while unattended in vehicles and they want to "save" other parents.

As a parent myself, I think these rules are absolutely bonkers. Kids might be less safe these days in hot cars because windows are now automatic and not manual, but there's likely a technical solution to that problem that does not require jailing anyone or ripping families apart because they ran in to get a coffee.

[1]: https://www.kidsandcars.org/