Is binding IsEnabled optional when binding Command?

Question

I noticed that the following code:

<Button Content="_Timbres..." 
    Command="{Binding Path=ShowTimbresCommand}" 
    IsEnabled="{Binding Path=CanExecuteShowTimbresCommand}"/>

behaves equally as:

<Button Content="_Timbres..." 
    Command="{Binding Path=ShowTimbresCommand}">

Meaning that the CanExecuteShowTimbresCommand is automatically bound to the IsEnabled property. Is that true and why?

Answer 1

Usually controls which accept a Command will set IsEnabled to false if the command's CanExecute is false, that's all there is to it.

MSDN:

Another purpose of commands is to indicate whether an action is available. [...] A button can subscribe to the CanExecuteChanged event and be disabled if CanExecute returns false or be enabled if CanExecute returns true.