Agreed. I think it's wild that such a position seems relatively common in the US (though at a surface level I understand that it's just a cultural difference).

The only situation in which I would consider charging my kids 'rent' is, if as adults, they were being irresponsible with their life, e.g. being a NEET and not helping out around the house. Even then I would hold the money in a separate account to gift back to them later.

I think it's parents' role to always be a source of almost unconditional comfort and security for their kids. Though I also think that this is unsustainable unless kids also do their best to maintain and respect that relationship.