I think the grand parent sees root as a risk 'cause it introduces additional level of complexity which could contain potential exploits. Superuser app is not bulletproof and may contain bugs. There is also a human factor. How many of us managed to dismiss a dialog box without actually reading them? I know I did not because I click everything, but because those thing may popup at most inconvenient time, when you want to click on something else.
To keep root or not to keep depends on users' needs. I just wanted to point out that it is not necessary to keep it once the job is done and it is no longer required.