You have clearly only met consultant version 1
Version 1 consultant does not need any time to understand a new customer's business because he has already selected the solution. The solution is the one that the consultant gets the most commission on.
Version 2 consultant does exist and a few of the more competent PHBs are able to hire them. Version 2 spends the morning listening to various employees until he works out which employee actually understands what is going on and how to fix it. He then listens to that employee and puts what he hears into a report for the PHB. The PHB then announces the content of the report as his plan (stop preventing the skilled employees from doing a proper job).
I was lucky enough to meet a version 2 consultant early on and so discovered the technique required to get PHBs to listen: increase your hourly rate.