The numbers are probably getting worse because society at large is becoming more tolerant of drugs.
I don't actually care how much this is costing nor how inconvenient people at HQs find it - I consider it to be a working deterrant for the small number of idiots who are, nonetheless, possibly responsible for bolting safety-critical equipment together, controlling aircraft, directing aircraft, handling weapons and other things that we in the military have to do that Joe F**kwit hanging around outside the local dole office doesn't. Fancy driving up to an armed guard who might have an Acid Flashback, or who is still a little too spaced out after last night to remember to put the safety catch on do we?
I suppose we could test this hyposthesis by "stopping" CDT for a year or so then "re-introducing" it.
One thing we really ought to consider is getting more DAPO roadshows going. I believe there is now only one guy doing these for the entire RAF, and he has his work cut out just doing the rounds of the trg bases: couldn't get him for love, money nor drugs to come to my last unit for a Friday afternoon trg period. Saw the show a good few years ago now, and it certainly made me pause for thought - even more so now I'm a Dad. If they showed half the photos we saw to kids I reckon a few more might not "try it out" (accepting always that they'll sooner listen to their idiot mates than someone telling them how it is).
TW - what makes you think you won't now get breath tested after an accident here? ATC and FC are also subject to these rules now.
ADIS - beat me to it.