Leds produce less heat per lumen than incandescent lamps, but the heat build up in the light fitting tends to be higher. This is why even cheap LED torches are often aluminium. The aluminium casing acts as a heatsink for the emmiters.
LED diodes do not have a heatsink in the raw component stage even emmiters that would only last a few seconds without any heatsink.
When mounted however they require careful consideration of how the excess heat is removed. Sometimes this is accomplished by driving the LED at low current levels, but more efficient heatsinking allows for much higher light outputs. This is why so many LED torches and purpose designed masthead lights like Lopolights are aluminium.