This is to protect and preserve existing settings (already edited) by the install script. It is a measure put in place due to occurrences of premature script exit on the install. That
/root/tmp directory is built in order to compile things such as ffmpeg, rutorrent .. etc.
example: #L513 Line # 513 in the setup script
It's probably not the most elegant solution, however, if you feel that you can provide a greater logic on the matter, remember -- we're a community developed resource. Please don't be discouraged from making a contribution to the code.
I will say in the end however that this provides no lack of efficiency to the install and is our given attempt at trying to keep the install on various providers and solutions as universal as possible. Sometimes we must sacrifice common logic to achieve a large base of versatility.. I know.. again, not the most elegant.. but hey, this is our spare time