It’s quite rare that a customer knows exactly what they need; often, if they do, they build it. The wins happen when a customer knows what problems they have,

It’s quite rare that a customer knows exactly what they need; often, if they do, they build it. The wins happen when a customer knows what problems they have, and you can present a solution that solves them better than they could otherwise get elsewhere. Otherwise, as you say, they will build it or buy it elsewhere.