All companies exist to provide profits to their owners.
Your argument about the datapoint can also be argued for lending: credit disappears when it’s most needed. It must be completely and utterly useless, then.
Or perhaps when a crisis strikes, if you want to minimize spending, you first eliminate consultant bills, instead of, idk, firing internal employees?
Part of the value of a consultant is that they are more mobile than an employee, so they get to see the same problem in different companies, and get expertise on that issue more quickly that if you stay on the first company in which you solved that issue. I’ve dealt with the same very-specific software on about 20 different banks, for example (disclaimer: I’m a consultant :) ); I have people under 25 on the team that are real experts on very specific things, and run cicles around people with 2x - 5x their experience if you count it in days and not problems solved.
And then of course consultants are sometimes hired for the wrong reasons and asked to do obvious recommendations. Politics were there before the consultants arrived.