Why LED lights must have cooling holes(1)?

Because this is determined by the characteristics of the LED itself. LED is light-emitting, and there is a thing in the diode called PN junction, which has unidirectional conductivity.

At high temperature, the "performance" of the PN junction will become weaker, and the LED light source shows that the light decay is relatively severe.

Therefore, compared with incandescent lamps (halogen headlights on cars are also a type), LED headlights are more sensitive to temperature changes, have lower tolerance, and are more likely to cause light decay (that is, lower brightness).
In addition, we say that LEDs have high efficiency, which is compared with incandescent lamps. The efficiency of the previous incandescent lamps was too low. The efficiency of converting electrical energy into light energy was only a few percent, and other energy was converted into heat energy, so it was very hot.

The light energy conversion efficiency of LED is high, which is ten times or even higher than that of incandescent lamps, and the energy of low power can reach about 40%. But the other 60% of the electricity will still be wasted as heat. That is to say, although the LED has high efficiency and less heat dissipation, it still emits a lot of heat.
The answer to this question is obvious. LED headlights will emit a lot of heat when they work, and high temperature will seriously affect the performance of LED headlights, so its heat dissipation is the top priority in the design. In fact, the current LED headlights not only have cooling holes, large-area heat sinks, but also cooling fans.