Because there's no need.
LED-based lights usually have a good combination of a bright hotspot with a wide spillbeam, giving you the best of both worlds anyway.
LEDs also make it possible to have variable output and as you increase the brightness you'll see more in the spill, effectively widening your field of view. Not exactly the same as a variable focus, but it achieves a similar effect.
Incandescent lights like the good ol' Mag had to cope with the fact that the emitter was not a point source - the filament in a bulb has a finite size, making it difficult to get a smooth and uniform beam. The variable focus on the Mag was an attempt to cover up the crappy and very uneven beam. (If you haven't used one for a while, just pick one up and try it - you'll be shocked at how poor the beam is).
LEDs on the other hand, are much smaller - closer to a point source, making it possible to get a smooth beam. So there really is no need for a focusing or adjustable reflector.