I'm reminded of a redditor commenting how he visited a music festival in Sweden as a foreigner, and how annoying it was for him, because all the food stands were expecting the Swedish payment system. And he couldn't even ask other visitors to buy stuff for him and take his cash, because the Swedes were very cash-averse.
Most people nowadays carry very little (if any) cash. However, I really doubt it would be a problem to find someone to buy food for you if you give them cash.
Except for supermarkets, I don't expect any stores to actually accept cash anymore.
This have lead to a growing bag of small change that is not leaving my home, so I can understand people not wanting cash :)
You don't need to be a Swede to get bankid, but you do need a national registration number which you can apply for if you intend to live in Sweden for something like a year or more.
In other words, if you live in Sweden you'll likely have bankid. As a tourist or seasonal worker, not so much.
Smartphones are now cheap as dirt. The bigger problem would be having a bank account.
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