It really is amazing how people seem to forget that an actual human being is the one ringing up their various and sundry goods at stores. Once a person steps behind the register, I guess we become robots, there only to serve.
For the record, the answer to the question "How are you today?" is not "Marlboro lights." And I don't know if wolves raised you or something, but I'm pretty sure most people were taught to respond when someone says hello.
What makes this terrible is that a lot of the people ignoring cashiers were once in the retail business themselves and have felt just how soul crushing it is being constantly ignored by your fellow-man.
Enthusiasm or a huge grin isn't necessary; chances are I feel like shit too. I'm at work, it's par for the course. But your life isn't so bad that you can't at least say 'hey' to your poor cashier. And for the love of humanity, if she says she can't take your check, don't throw your cigarettes at her.
I'm asking for a stun gun for my birthday.