As with most things, it depends on the location.
Most of the time I don't even lock my bikes (breakfast with the club, bathroom or snack breaks). When I do, I have a cheap combination cable lock for the commuter, and an even flimsier lightweight cable for the roadie.
I certainly wouldn't do this everywhere, nor if I were going to be leaving the road bike for several hours, or the commuter overnight. But it's plenty for errands and for dinners out, in the places I ride. The people I ride with do exactly as I do, and none of them has ever had a bike stolen under these conditions.
My assumption from that picture wouldn't be that the person doesn't know what s/he's doing. It would be that the person knows what s/he's doing and where s/he's parking the bike.
Speed comes from what you put behind you. - Judi Ketteler