We say no when the project doesn't make sense.
It's the most useful thing we can offer and the rarest to find in a commercial conversation. There are situations where a mature vertical product costs less and works better than anything built to measure, and others where an organisation's problem isn't software but a process nobody wants to change.
In both cases we say so, even when it means turning down a project. That isn't generosity: a wrong project costs us more than it costs you, because it consumes team time and produces an unhappy client who was right to be unhappy.
The practical consequence is that a demo can end with "in your case, look elsewhere". It happens, and it's a legitimate outcome.