There are a lot of situations where people talking on the phone to other people is annoying and rude. I expect there's substantial overlap with the situations where people talking out loud to Siri is annoying and rude.

And for the most part those situations are not ones where the presence of QR codes would be of significant benefit.

Note that I think QR codes are great for things like airline tickets or baggage tracking tags.

How is using a qr code to get a direct link to what you need even comparable to doing a search on that object and hoping you get relevant information?