I use a small, USB connected Wacom tablet and find it indispensable for fine masking, shading, dodging and burning and cloning and healing.
There is training of motor skills to become dexterous with it. One difference from a mouse, at least with my tablet, is the position of the pen on the tablet has an absolute correspondence to the curser's position on the screen. This is different from a mouse, where the curser remains stationary and restarts the cursor where it left off when you lift the mouse off the pad, reposition it and start using it in the new position.
While PS and LR are getting enormously better, the automated selection tools are still not perfect. For example, Subject Selection often leaves gaps in the mask between crossed legs or akimbo arms...Or when the subject is shadowed, slightly out of focus or small in the frame.
The pen and tablet are much better than a mouse or trackball at precise editing of small, fine features. Just keep the mouse handy for everything else.