The aircrew "should" wear them, but many refuse because they think that they are above all that (or too idle to put theirs on).
Or perhaps we think they look f

g stupid on a camouflage uniform!! This is H&SAW madness. Heathrow, maybe - V busy out there. Brize with its one movement every half hour?!?
I saw a bunch of IOT cadets at the College a while ago marching to work. A flight of about 20 of them. They were all in DPM kit and carrying webbing with their high vis jackets draped over the back of each rucksack. Military bearing - I don't think so! The chaps on the back rank
might be acceptable, but all of them!!

Grow up, we are supposed to be the military not a bunch of road workers.
I'm with Gnd on this one. HSAW is about risk ASSESSMENT. If you think the risk is already negligable (and lets face it just how many personnel have been run over by aircraft or vehicles on the apron?) then that should suffice. This is another example of jumping on the "civilian best practice" instead of applying common sense. It's all about awareness and application of a bit of common sense.
Oh and as Gnd said, we need a few more men to take over and challenge the HSAW nonsense.