There are several disadvantages to the POS system, including the increased difficulty teaching the system and cost. POS systems are generally more popular today than before, but many stores still rely on a cash register due to cost and efficiency.
A cash register has fewer components than a POS system, which means it's less likely to be able to be used for payroll, worker data, recordkeeping and other normal business operations. Because of that, the cash register is much easier to learn. There are fewer ways to make mistakes, and there are not as many programs to worry about on the machine.
Small business owners may first start with a cash register and avoid moving on to a POS system. That's because cost is a major factor for those looking into cash registers versus POS systems. A new cash register is typically less expensive than a new POS system, and when this is combined with the extra training costs, it can result in stores sticking with a cash register-based set up.
Others may simply not need all of the capabilities of the POS system. If payroll is done on paper or sales are processed nightly by the staff, it can make the POS system look too expensive for the added benefits that aren't needed.