As a SUPER you can't impersonate a user to see what access they have without having a secondary login. 

oftentimes troubleshooting an ssue is made difficult due to user personalisations, and the exact arrangement of their screen even with a seperate account cannot easily be replicated...so impersonating provides the ability to see what the users sees (yes screensharing can be done too but we also find operations users need to actually get on with processing other things, and leave service agents to troubleshoot root causes and do the investigations).

If a user is impersonated, then a record of that this action should be recorded in record retention/changelog for audit purposes