One of the problems with LEDs, including all diodes, is the forward voltage drop has a negative temperature coefficient, so the current tends to rise, as it heats up. If a constant voltage source is selected to give the rated current, when power is first applied, then the current will rise, causing excessive power dissipation, resulting in destruction of the device.
You could power it from a voltage which would result in a forward current below the maximum rating, even when the device is operating at the maximum resulting junction temperature, but that could be tricky as the forward voltage for different LEDs varies.