We regularly get requests from clients and prospective clients who say that they want a content management system for their web site. However we find that few clients that take the time to manage their content.
Some our clients do take the time to update their web sites. However, more often than not, the content is not updated as the client is too busy running a business to do the updating.
Content management systems require extra work to set up when compared to a web site that is updated by web development professionals. Search engines may have issues with finding all of the content. And if the updated content is not proofed, it can contain embarrassing errors.
This is not to say that content management systems are useless, only that if you want one you need to have the time and discipline to use it. Properly done a user updated web site can provide up to date information and fresh content which grows and grows providing rich source material for search engines.