The article was well written, but probably extremely basic for people who read this site.

One thing I will point out is that you may want to make backups of the system databases in most real world situations. If you have no user defined information in your system databases, then backing them up may be worthless, but that most people do.

Remember that information such as defined operators, sql server agent schedules, and certain types of replication information are stored in msdb. Also, (whether this is smart or not is a completely separate topic) some people put utility procedures and functions which are used for server maintenance or used for multiple other databases inside of the master database. Your model database may be highly customized for your situation if you are doing certain types of analytics that regularly create new databases. So, for most real world situations it makes sense to backup at least some of the system databases.