A question

If a company hires an expert to do a specific job, why reject all their suggestions? I don't see the sense but maybe it's logical in bizarro world.

You hire an expert on kittens, for example. You pay a lot of money for their expertise. They provide a sensible plan on the care and maintenance of kittens. They work at it for months. You've shelled out thousands of dollars and then you decide you know best. You reject all of the expert's suggestions.

Personally, I don't get it.