Cognitive function testing has been under research for decades and progress has been made in defining measurable parameters. The difficulty seems to be in finding consensus on an acceptable objective standard for defining the parameters for acceptance or rejection. Meanwhile most societies will continue to apply the arbitrary BAC as being the standard for acceptance or rejection for vehicle operators. Perhaps someday a more objective cognitive function standard will be applied which recognizes cognitive function impairment causality is not limited to just the socially stigmatized acts of being impaired by alcohol or drugs.
Dr Mark Rosekind (along with others) has participated in fatigue research and as an NTSB board member, has advocated for further recognition of fatigue as a cognitive function inhibitor. Perhaps someday reason will prevail over the entrenched attitude that fatigue is just an excuse for the lazy. If a pilot is tired he or she needs to be careful how they broach the subject lest they be referred for a medical "sleep study" or become subject to being disciplined for absenteeism!
The tide of general opinion is influenced by reason and ignorance, and generally shifts very slowly, but is progressing in the right direction. (very slowly)
Even with all that said, taking a drink (or several!) is still a conscious choice made by the individual concerned. A pilot is expected to make responsible choices wherever they may affect one's suitability for flight duty. Screwing up once and having to call off sick or fatigued is an error. Doing it multiple times is a pattern of behavior and probably indicates the need for some sort of professional help.
I had a guy show up at the airplane for an early short notice call out for a charter flight. He was by my estimation about half in the bag. I told him to go away and that I wouldn't volunteer that I'd ever seen him that morning if he would call the CP and explain why he couldn't fly today. The CP called me 20 minutes later to tell me the guy had resigned and that a different FO would be arriving soon. He asked after my own "suitability for flight" and I told him that the 4 hours of sleep I'd had would likely be sufficient to carry me through to about noon before I'd have to check into a hotel to get some more sleep. The trip was scheduled to be completed by then so no problem as long as it didn't involve alcohol!