Seems like a good defence in depth strategy. These days most systems have a pretty good boot chain security, so after a reboot you know the system is in a valid state and any potential malicious changes have been flushed out.
Sure they would. If the system was for interactive use, it likely requires some login or unlock password. If the system is supposed to respond to external events - such as receiving phone calls when the system in question is a phone - then a reboot will effectively disable it until the user notices.