The device's MAC address isn't available under iOS 7 and later

For privacy reasons, Apple has removed all the ways to uniquely identify iOS devices and users. In iOS 6, the UDID unique identification number was removed, and starting with iOS 7, access to the MAC address was removed too, as it is also unique and could be used to track users. For this reason, the MAC address isn't shown for the device on which Network Analyzer runs.

You can find the MAC address in iOS settings under Settings → General → About.