Multiple factors affect the loss of licence and disability insurance rates.
Yes, the single greatest cause appears to be stress and or the secondary effects.
The single biggest cause of stress among male pilots is caused by societies incorrect views that males should not be parents and, that females should have absolute power in parenting and property.
In Canada all the pilots I've met that removed themselves from flying did so for medical reasons, and in particular, family court decisions that effectively removed them from the lives of their children. Its this last factor that has unnecessarily destroyed many a pilot's career.
Most pilots love flying and I think it would be a very small percentage that would want to rip off the rest of the population and end their own flying career.
The US has a government policy of cross-checking recipients of disability payments to pilot licences.
As for random drug and alcohol tests, I could not agree more.
It is that lack of random operational checking for drugs and alcohol that encourages its use. Random testing with hair follicle testing before and during employment is the only deterrent.