Tales from a parallel world.

It seems to me that Asians (except for the Japanese) generally try not to complicate their lives with overly complex and obscure rituals and thoughts.
Here, everything is simple, logical, and follows the path of least resistance.

The culture and way of life of a people are absorbed and adapted from the surrounding actions.
The same street cleaning that you described is a mini-cleaning of the streets during the rainy season.
And so on. The deeper you study, the more interesting patterns you can find.

Consequently, the more complex the living conditions, the more sophisticated methods are used... and over time, the custom remains, but the original reason is lost.
This is how civilizations arise in borderline-difficult living conditions. And in simple conditions, there is no such natural incentive for the development of progress.

Regarding taking bread with your left hand, try proudly and loudly declaring that "you wash your hands!!!":D

An excursion into a parallel world is quite interesting.