why problem interviews are so great

In his book, Running Lean, Ash Maurya recommends validating the problem you want to solve by interviewing potential users/consumers. His idea is that you can get a strong signal about whether the problem is really important, even from as few as 15 people who would be early adopters of your product or service.

In addition, what he calls the problem interview enables you to meet and recruit potential users, and get them to recommend others who might like to participate. This is great, of course, but a third advantage to problem interviews is that you can discover problems you hadn't thought of yet, or realized were important.

All of these outcomes of the problem interview are extremely useful in determining whether there could be value in developing a solution. Nonetheless, part of the art of problem interviewing is to ask questions which will allow you not only to validate your idea, but to get new insight. Also, it's important to be open to the possibility that the problem you've defined isn't worth solving based on the strong signal you've received. But if you took good notes, and paid attention not only to what people told you, but how they said it, you may be able to look back and find something really worth pursuing.