That is a false assumption.
There are many cases where KM processes can or should become mandatory, and that the volunteering of knowledge as part of these processes can or should become an expectation.
Let's take the realm of Project Management. Every project delivers two workstreams, the Product Delivery Stream and the Knowledge Delivery Stream. Much time and attention is paid to the former - non-delivery of the product is not an option; the Product Delivery Stream is mandatory. Far less time and attention is paid to the latter, and the delivery of knowledge from the project is often treated as optional - an afterthought, to be done if you have the time and energy and inclination.
And yet the knowledge stream is often extremely valuable - in some cases more valuable than the product stream. Take the Pharma world of drug development, for example. 97% of drug development projects do not result in a commercial product; the only valuable deliverable they can offer is Knowledge.
In a situation such as this, do you allow the Knowledge Delivery Stream to remain voluntary, optional and ad hoc?
No - you make it mandatory.
You embed Knowledge Management processes as required elements within the Project Management framework. For example you require
- Every project to develop a knowledge management plan (or learning plan), and demonstrate this to management
- Every project to conduct at least one Peer Assist to gather knowledge from previous projects
- Every project to conduct a Lessons Capture meeting at major milestones or project stage gates
Then good facilitation can ensure that the people who turn up, freely volunteer the knowledge they hold.