I was gonna mention that, but I felt I was waffling on a bit, so I deleted it!
We've got the same thing with GST, basically like VAT or sales tax. So that'll appear on the invoice from AliExpress or Steam or wherever.
Businesses have a threshold before they need to charge it though. If they're under that threshold (like a small business), but the value of goods is over another threshold, then the receiver has to pay GST.
If I remember correctly, customs would mail me a letter, and I'd pay it like a tariff. Which brings me back to the main point, that's just that the carrier has nothing to do with it. It's ridiculous to get them involved in a transaction they're not a party to.
Process might be slightly different, I'm remembering from about fifteen years ago.