
This is of course very much essential because this is the wisest decision when the management feels they don't have sufficient resource or skill to handle the nature of the new project or contract. But if always the answer is NO, in that case the company will never get any contract. So, it is correctly advised by those guru to say NO only when you feel that you don't have sufficient skill set or bandwidth to cater the project or even the nature of the contract.
By saying NO in this situation, helps the organization to save from getting blamed in case of unforeseen failure.
But if you, as a CEO or higher management authority, ever decided with YES to get the contract, you wouldn't have any choice to say NO ever in the entire life cycle of the project. So, to be a successful company, it is very much important to decide with YES or NO.
As a very practical case, if a particular company, grabbed a floating tender eying to make a profit even without considering its skill set, that should not say NO in the rest of the phase of the project and must try to meet all the requirements of client (/s) even in the case of extreme resource or skill set crisis. Otherwise, the corporate may loose all its credibility.