Pro Bono Consultants, do you use them?

How many of you out there, or how many of your companies, have every used, or considered using Pro Bono Consultants in your Procurement/Sourcing Projects? I have done a few projects for "nothing", either as the whole or part of a collaborative team, and I find doing this invaluable to my own personal development, maintaining and improving Procurement Skills not required in my current role, exposure to different industries and company types to name a few. And from the feedback the companies definitely benefited as well. The utilisation of these types of consultants/consulting services doesn't seem to be well advertised or greatly utilised, is it because we still believe "there is no such thing as a free lunch"? Would you use a Pro Bono consultant/service to achieve your Procurement Department goals? If not, why not? Do you think reaching out for assistance as a sign of weakness, or would look bad on you in some way? Would be interested in your thoughts and opinions, thanks for sharing...