Ross: Hey. Oh, oh, how'd it go?
Phoebe: Um, not so good. He walked me to the subway and said 'We should do this again!'
All: Ohh. Ouch.
Rachel: What? He said 'we should do it again', that's good, right?
Monica: Uh, no. Loosely translated 'We should do this again' means 'You will never see me naked'.
Rachel: Since when? Coyote
Joey: Since always. It's like dating language. Y'know, like 'It's not you' means 'It is you'.
Chandler: Or 'You're such a nice guy' means 'I'm gonna be dating LEATHER-WEARING ALCOHOLICS and complaining about them to you'.
I think Mike's answer is entirely sufficient.
Just because people put words together, does not mean that some "specific" meaning" can be derived from what they write or say. This is a case of poor communication skills on the part of some author.
"Leather wearing alcoholics" is not an identifiable social convention.
What the author may be referring to are people who are both "drunk" and "wearing leather" as
Bikers or other rough sorts of people do to create a social identity.
Referring to "alcholics" is an extremely vague reference, because it refers to persons
who have no control over their alcohol consumption.
As indicated by the American Medical Association, Alcoholism is classified as a medical diagnosis.
The end result of this is that we can see, eventually, that just because a person is wearing "leather," it does not mean that the person is has an Alcohol Problem.
Not everyone drinking alcohol is an "alcholic".
As one popular joke informs us, the fellow says:
"What? Me have an alcohol problem?
I drink. I fall down. No problem!"
She's just sticking together a couple adjectives; "leather wearing" and "alcoholic" (turned into a noun).
Actually, I suspect Chandler may be making a disrespectful reference to stereotypical aspects of motorcycle culture. The idea is that, supposedly bikers drink a lot and wear leather. The leather has to do not just with culture, but with practical aspects of riding motorcycles.