Changing the organization
Why would an organization want to adopt the Cleanroom approach when it can get the same work done using their current SE strategy?
The traditional methods of developing software are so deeply ingrained in many software development organizations - the inevitability of discovering bugs is looked upon as "normal". The organization that wishes to adopt the Cleanroom approach must be ready for a "culture change", or as in Dr Harlan Mill's words, adopt "non-error as part of the company culture".
Since the primary objective of Cleanroom is to prevent errors, the final product is near defect-free with a scientific certification of reliability. This lowers cost to produce and maintain a product by a large factor.