This feature makes it easier for people unable to use a mouse to use the user interface.
The behaviour of focus on one's desktop can be governed by policies in window management.
Another common policy on Unix systems using X Window System (X11) is the "focus follows mouse" policy (or FFM), where the focus automatically follows the current placement of the pointer.
When text is entered into the component, it will appear at the position of the text-cursor, which will also normally be movable using the mouse pointer.
Conversely, giving the right thing focus can significantly enhance the user experience.