With an installed OS, the disks are exposed and it would not be as
secure. An installed OS records status in the logs and searches the
disks for commands, and so the disks must be accessible - i.e. you
cannot unmount them while you are actively running programs in an
installed OS environment like being connected to the Internet and web
surfing. For example, where do you think new bookmarks are saved? On
disk, of course, like in a bookmarks.html file. I just happen to save
my in-Ram browser environment after each session onto a mounted disk
after my connection to the Internet is shutdown. A small price to pay
for the increased security - its just a few commands.

Security is a figment of the imagination anyway. I'm sure a
determined cracker can get in anywhere they want - but, when they do,
they either have the skills or don't, and most crackers don't. I
happen to like not having my disks exposed for that extra measure of
obstacle for any malware that gets past my restricted firewall. And
when I power down, the malware in-RAM file system is kaput!

Since I have a steep background in system software engineering, I am
not the average user. Doing this is a piece of cake to me. It takes
only a few commands to access my hard disk, pull the initialization
scripts over to the Live CD environment and then initiate a connection
to the Internet - less than 1 minute after it boots up.