I take a keyed lock and cable when I tour. I rarely lock the bike when I go into a store, but I do tie a piece of rope around the frame and front tire so no one can run off with it and put it where I can see it.
When I go into food stores, I often ask if it is OK to leave the bike at the front inside the store. There usually is someone who bikes that works there and says “sure, no problem.”
Once, in Sicily, I was told to leave my bike outside the B&B where I had booked a room (and told them I needed a secure place for my bike). I did this and when the manager left, I went down, undid the S&S couplers and brought the bike into the room and stashed it into a closet.
I wonder if uncoupling the bike and locking the parts together would be a way to stop thieves?