Overall there should be no reason to move them unless you just want to. As long as you are doing full backups of the system databases on a regular basis (AND testing them) you should be fine in the event of a crash. They are not really "synced" with the user databases. The master database stores all the information about the user databases so you might back this up more frequently than the other system databases if a large number of changes are made to user databases.

The tempdb is a database that changes often and is not required to be backed up. DBAs usually place this on it's own drive for performance reasons. It just depends on the load your instance has on it if you want to do this or not.