''So what bad has this option done?'', you probably as yourself. Well, not much, but I find it evil because it confuses people, especially those new to SQL Server. I have many times seen people specifying something like 3, and expect SQL Server to keep the three most recent backups in the backup file and overwrite everything which is older than ...

How often do you do this? Look over each message (type) in the errorlog file and determine whether this is something you want to act on. Sure, some (but not all) of you have some monitoring solution in place, but are you 100% confident that it really will notify for all messages that you might find interesting? That there isn't even one little ...

This can for instance be very useful if you want to keep track how long time things take, over time. Check them out here.Version history here.

Just a quick note that we again can modify whether system messages are to go to eventlog/errorlog again. I.e., we can change the is_event_logged column in sys.messages. This is very valuable in general and specifically is you want to define Agent alerts (for which Agent polls the Eventlog). For instance: SELECT * FROM sys.messages WHERE ...