A lot of places where I pay by PIN they still swipe it afterwards so that they have a record on their own system (not sure why they need this though) - I think this is what OP refers to.
The difference between US banks and mine though is that if I try to pay by signing my bank won't authorise it - I have to enter my PIN (and sometimes sign too) to make a payment.
Payments online is more of the retailers fault though. They shouldn't accept payments where the CVV check or address check fails. Here in the UK most retailers won't accept payments unless it all matches up, but as I understand this isn't as common in the US.
The difference between US banks and mine though is that if I try to pay by signing my bank won't authorise it - I have to enter my PIN (and sometimes sign too) to make a payment.
Payments online is more of the retailers fault though. They shouldn't accept payments where the CVV check or address check fails. Here in the UK most retailers won't accept payments unless it all matches up, but as I understand this isn't as common in the US.