The built-in storage media, such as hard drives, flash drives, and RAM, accumulate several gigabytes of data over time, e.g. personal data in address books.
The data saved on old assets might reach the secondary market. This is a particular issue if you have a legal duty to keep third-party data confidential. Attorneys, tax advisors, doctors, and HR departments are just some of those subject to such requirements. Only an erasure certificate can trustworthy proof the deletion of the data.
Printer software can be reset to its default factory configuration.
While this deletes all of the changes made to the printer settings, it very rarely erases data from the storage device.