Final answer:
Starbucks stopped requiring signatures on credit-card purchases under $25 to reduce transaction time and improve efficiency.
Step-by-step explanation:
Starbucks stopped requiring signatures on credit-card purchases under $25 in an attempt to reduce transaction time. By eliminating the need for customers to sign for small purchases, the checkout process becomes quicker and more efficient, helping to reduce waiting times for customers. This move can also help reduce the workload of employees as they no longer need to handle signatures and can focus on serving more customers.