Many large companies offer those kind of services for free because they are already included in another service that you are going to purchase, or, in other cases, because they don't give much importance to this crucial process.
Which is, in fact, necessary: from the assessment (or check-uo), we are able to create the document where we suggest improvements, action plan and delivery times.
Based on this document, your company is going to plan al the further activities.
An high level evaluation is a great and essential starting point to draw a strategic planning which is going to help your company achieving its goals.