Old King Coal
Yes the numbers of drivers killed in accidents related to drink is low. But then one is too many.
You ask how many passengers are killed by pilots who have been drinking, no idea, but again one is too many. Which is the point of this legislation, to stop it happening not nesseserily to reduce the number.
I could ask how many people have been committed Treason in the last 30 years? I can think of one, does that mean there should not be legilsation to prevent it? Of course not.
At the end of the day, whether you like it or not, the public don't want to be flown round by people who have been drinking. Aircrew/ATCO's and engineers are all professionals, and in positions of responsibility for which they are well rewarded finacialy. If you want to drink don't fly and if you want to fly don't drink. The final choice is if you do both then expect the penelties.