Coffee Or A Coffee?

I've been hearing more and more people say "Let's get a coffee" now. Before, people would just say, "Let's get coffee." Why the addition of the article a? Is the article even correctly placed?

I think people say "a coffee" now because of the many coffee shops and coffee varieties available. When the article a is used, it means that the speaker wants one variety out of many (a bag out of so many kinds, a book out of the many available, a drink out of so many varieties of drinks). So, if the person says "Let's get a coffee," he or she wants one kind of coffee out of many (cape barako? African coffee? black coffee? coffee with cream? decaf?). Or, "a coffee" could also mean the types of coffee that come out of coffee preparations and recipes (latte? mocha coffee? French vanilla? espresso? cappuccino? caramel machiatto?). Thanks to Starbucks and all these lifestyle coffee places, we can now say "a coffee."

If you want to say "Let's get coffee," it's still all right. Truth be told, the article doesn't make much of a difference anyway.

I don't drink coffee, though.