> You may need to authenticate payments a dozen times in an hour one day, when you are on a farmers market which doesn't take card payments or you are out dining with friends, and another day not at all.

It's very unlikely people would need to mess about with MittId/BankID if they can't use card payments at a market. Firstly, if they're doing the almost-unheard-of clunky approach of using their mobile banking app to make a bank transfer, it would probably be authorised using their touch/face ID instead of BankID/MittID. But far more likely, they'd use one of the ubiquitous mobile payment apps: Vipps (Norway), Swish (Sweden) or MobilePay (Denmark).