Most people have a credit or debit card. The few who only have cash will be out of the food/beer/merchandise line off to the side somewhere getting their re-loadable card while everyone else moves through the line quicker. Employees cant steal cash or count change wrong...counterfeiters can go kick rocks.

I only carry cash when i go somewhere that i might tip. Lately though i have just been putting that on the card too. Everything i buy has a digital-paper-trail and consumer protection.