Core question
Why do AI vendors skip the diagnostic step?
Short answer
Because a well-scoped diagnosis takes time and often reveals that the organization is not ready for what the vendor is selling. The vendor loses the sale. The organization keeps the problem. The incentive is structural, not dishonest, which is exactly why buyers need to insist on the step themselves.
This is not an accusation of bad faith. It is a description of how incentives work.
A vendor's product is a solution. Their sales process is designed to establish that you have the problem their solution addresses. A genuine diagnostic can conclude that the constraint sits somewhere else entirely, that the data layer cannot support the output, that the team cannot sustain the tool after deployment, or that a simple process change would produce most of the benefit at a fraction of the cost. Any of those conclusions costs the vendor the sale.
So the diagnostic gets compressed into a discovery call, which is a qualification exercise wearing a diagnostic's clothing.
The vendors pitching you right now do not need you to run that diagnostic. Most of them would rather you did not. You need you to.