You’re right, the event receivers are a good option when you want to perform some actionable task (ex: kick off a workflow or execute some custom logic as a result of the event you’re trapping for being fired). You could even write code to log all changes that have occured to a given list.

The problem with this approach is you’ve have to implement event receivers on each list you want to track actions on and have to manually code up the "roll up" logic to log centrally. The snippet above uses SharePoint’s built-in logging to track all of these actions for you without you having to implement custom code to essentially duplicate the functionality.

Think of the Windows Event Log and how Windows essentially logs system messages to it automatically and how difficult it would be to write code that captures *all* Windows events you care about. In this scenario here, he wanted to essentially know what’s going on in his site collections. The code snippet above provides this functionality without too much pain

Just looking at options at places to do routine tasks when user performs operations on a list item.