I get that and totally respect it, and I never pursue further conversation unless I get a chatty vibe from the customer.

However it's insanely rude to ignore me to my face after I've just asked you a question. If someone answers "Fine. Cappuccino to-go." that's really all I'm asking for. I'm not simply an interface through which you get coffee, I'm a human person, and I think customer service staff deserve to be treated as such.