There are newer solutions like iZettle for cards that costs less. In Sweden we also have Swish, payment by smartphone without cards, but that is also a bit harder for older people.
And yes, there is Swish/MobilePay, but that only really works if you're local. A tourist - even one from a neighbouring country - will not have access to that.
Costs per transaction are higher but for really small scale the ease of use wins.
There were iZettles in many Helsinki cafés a few years ago, but it seems to me that most of them have been replaced by normal PoS terminals.