Capturing business requirement is a cumbersome process in many aspects. For some it might become difficult to capture concrete requirements if business is not process oriented and documentation centric. In such conditions there would be as many statements misaligned with each other as many mouths. Each member engaged even in a similar or same process might talk differently regarding the same process which could lead to a big confusion. In such conditions everybody would be eager to speak but nobody to vet the stated requirement.
In certain other conditions, systems in place could be too cumbersome that your timelines for closure of requirements capturing would definitely get shattered. Here, in this case, you would be running after the process owner, who would be rich in process knowledge and practical experience, but he would not be able to give you substantial time to help you in capturing requirements in multiple runs.
Requirement capturing goes useless if there are some ambiguities or misalignment that stops it for sign off. It is important to opinion from everyone who is part of a process in the organization and then a proper alignment needs to be done, if required, by involving top management into it.