Errrr the third picture clearly shows rather a lot of riders wearing helmets.
I can't believe someone took the bait.
The helmet wearers? It shows a few, not rather a lot. And as for that few apart from two, one of whom is on a tall bike, the others, to an man, woman, and child, are in team/club kit. Because they are team/club riders. Out on a team/club ride. And obliged by their need to ape their professional counterparts to wear helmets, and lycra. Thus demonstrating that they are serious cyclists. Adrift. In a sea of normal people, wearing normal clothes, doing normal things, like riding a bike. For which no special equipment is required here. Unless you are a bit odd.
Because here, and this is the point, wearing a helmet to ride a bike around the city is very, VERY, odd.