Why use the ComponentResourceKey MarkupExtension?

Question

I've written a lot of WPF styles and templates but never used the ComponentResourceKey markup extension. I've never understood why I would need it.

I obviously read this in the docs

Defines and references keys for resources that are loaded from external assemblies. This enables a resource lookup to specify a target type in an assembly, rather than an explicit resource dictionary in an assembly or on a class.

But I'm still not understanding what this buys me. Either way I have to specify the target type.

For example, reading up on creating a custom view for the ListViewControl, I came across this article which uses a Style that starts off like this:

<Style x:Key="{ComponentResourceKey 
      TypeInTargetAssembly={x:Type l:PlainView},
      ResourceId=myPlainViewDSK}" 
       TargetType="{x:Type ListView}" 
       BasedOn="{StaticResource {x:Type ListBox}}"
       >

If this were my project, why would I not want to just start it off something like this?

<Style x:Key="MyViewKey" TargetType="{x:Type l:PlainView}"