also, integrating the reflector and the bulb makes it easy to replace the reflector if it is damaged. of a bulb blows and gets stuff everywhere, you can simply replace the reflector easily.
when my e2e reflector was damaged, the whole head needed to be replaced.
furthermore, when you take out the whole lamp assembly, you can dissect it and use the reflector for mods! /ubbthreads/images/graemlins/grin.gif