If you have more than one person logging in, it's far easier to identify who did something as root by looking at the username that logged in.

Also far better to encourage running sudo for every command, gives a nice simple audit log of what happened, right there in your syslog, so you can identify and undo mistakes, and also eliminate lines of enquiry.

Clearly you can cover your tracks with the old sudo vi / !bash and similar tricks, but the goal isn't to protect against hostile privileges users, its to know what happened so that when John is on holiday you can see what he did to fix the problem you had last week.