There are several reasons for wiping devices:

Mobile devices like smartphones and tablets are becoming more full-featured all the time. This means it’s easier for your users to store sensitive corporate information such as personal identification or confidential communications and access it on the go. If one of these mobile devices is lost or stolen, wiping the device can help prevent your organization’s information from ending up in the wrong hands.

When a user leaves the organization with a personal device that is enrolled in Basic Mobility and Security, you can help prevent organizational information from going with that user by doing a factory reset.