It's mainly to reduce emissions and to protect the local environment. The paragraph also more generally states that you have to "prevent unnecessary noise pollution and emissions", which as we learn in driving school also means shutting off your motor when sitting at a red light.

So at redlights you need to turn off your car, then turn it back on when it changes to green

EDIT: Specify the part of the post that bewildered me.

Many recent car models do this by themselves nowadays.

https://en.wikipedia.org/wiki/Start-stop_system#History

Huh, that is really cool. Never heard of it.

Thanks for the information.