Suppose you have the need to create a custom control like I did recently
One of the things that you should do so people do not get confused about using your control is to “implement” any events in whatever you use as your base class that should not be exposed to end users of your control. If you dont inplement these events then a user could, and that might end up in surprising behaviour in your carefully crafted control.
If you dont implement the Open event for your custom control a user could put an instance on a layout and implement that event. If this causes problems than you can make it so they cannot implement the Open event simply by adding that event handler to your custom control.
There may be events, like ConstructContextualMenu, DragEnter, DragMove, etc that make no sense for your custom control and so implementing them in your class would make it so users cant.
And this should make your custom controls easier for others to use.