Most purchases (perhaps barring impulse buys) are made to fulfill a need or to solve a problem. Looking from a broader lens, problems can be of numerous types and deviate heavily from the traditional sense attributed to them. Every product worth its salt today is made to alleviate a problem after it has been recognized and established. Products which do not solve anything, do not survive.
Much like going to the doctor a customer who has walked into a store is looking to fix an issue E.g. a customer is not shopping for a drill machine but needs a hole somewhere. It is this problem which has forced a tool purchase. Much like doctors, sales representatives should be able to quickly diagnose the underlying problem of the customer.