LED's are most importantly known for their less power consumption. There are few other advantages of LED's, like less heat emission unlike incandescent and CFL, and no usage of lead, which saves the environment.
What you don't know is, that LED's emit less heat but the driver in an LED fixture generates a lot of heat. Which is a main cause of a failing LED light.
Now, coming to the actual question of why LED street lights should be switched off during day time?
We all know that LED street lights are used in an outdoor environment. These LED street lights are under direct sunlight during day time. As mentioned above the heat that LED light driver generates is a lot. Now, if the street light is kept on during the day, the heat absorbing capacity of the driver will be tested and if the heat increases the LED street light fixture will be damaged and will fail eventually.
So, it is important that the LED street light be switched off during day time, and why would anyone need it?
Solution:
Get an electrical timer from Legrand and set your desired time for switching ON/OFF the LED street lights.
Also, get LED street lights at best rates