Wikipedia's community editors work at maintaining the accuracy and objectivity of the articles, which requires identifying conflicts of interests and removing bias. Editing-for-pay can be a source of such bias, particularly when the edits are promotional in nature, or in the interest of a paying client.
In response, the Wikimedia Foundation is trying to keep articles free of promotional content.
While volunteer editors are not subject to the changes, it does affect employees of a gallery, library, archive, museum or any similar institution in instances where the edit is about the institution itself. Such employees, which can include professors, can continue to make contributions in their area of expertise without restriction, but must declare their employer for edits relating to them.