I have worked in many places where none of the kitchen staff knows how to program or change the POS system. This is a recipe for bad news and a food cost that can go through the roof even in a well managed kitchen. Even if it seems to be simple inexpensive errors, a side of fries instead of no vegetables, on a repeat basis, the small stuff can add up quickly. A side salad with no dressing or dressing/side gets sent out repeatedly with dressing on it, this salad can not be saved, its dressed and the salad wilts quickly.
An inexpensive side at $1.50 a pop, can quickly add up over time when line cooks don’t know or forget that X really means Y. Not to mention the time wasted for a waitperson to physically have to enter the kitchen, tell the cook that this salad has dressing/side and the time the cook wastes (especially on a busy night) noting this.
$1.50 X 100 times is not small change. Multiply this daily for a month and the small change equals thousands of dollars.
Not only does having a properly programmed POS system make sales and inventory easier to track, it cuts down on error, time wasted by waitstaff and by back of the house staff clarifying things and it can also impact tracking theft of product.
Point of Sale systems are wonderful tools, take advantage of them.