Im very sorry but people have to go to work to pay for their days off. I am not saying go to work pi55ed, but the system is attacking the wrong people. It is a demeaning experience to be tested for whatever. The very test gives the impression that you are a guilty party, fighting to prove your innocence.
You could take this argument in all directions. Say, you are lining up to take off and you think your partner has just air kissed you, walking out the door in a skirt she has never worn when you have gone out? Say, you are on short finals, knowing that, when you get home, their is that Amex bill for £XXXXX that you just haven't got the cash for. Are you 100% on the ball?
Give every pilot a faithful test.
Give every pilot a credit check.
You are easy targets, because if you refuse, then you must be guilty.