If you're headed to a craft establishment, $2 is the norm now. (aka a drink that has 4-10 ingredients, not a vodka/soda)
Personally if the drink is sub-10$, I tip $1.
Then you're not going to 'craft' establishments.
Maybe I'm not. Could you link an example of one? Would you tip more than 1$ on, say, a $6 drink there?
You wouldn't be paying $6 for a 'craft' style cocktail anywhere in the US. A 'craft' cocktail usually has 4-10 ingredients and a garnish that compliments the flavor - usually through your orthonasal senses. It's not a vodka soda or a gin and tonic. It's a Fish House Punch or a Jungle Bird or a Champs Elysees or any number of amazing cocktails that exist in the world.
I suppose that's where the disconnect is. I only order beers or shots of whisky. One dollar per drink keeps the bartenders attentive in my experience.