Pointing and selecting are two different tasks usually on one device -- the mouse. But it doesn't have to be that way.
You might want to use one method for the pointing -- hand, foot, head, mouth or even eyes -- and another for the click: switches or an automatic click from letting the cursor rest or "dwell" on the target
Whatever way you are moving the pointer to click on a target, Douglas Engelbart's invention in 1964 is the source: a wooden shell, circuit board with two metal wheels. Then Bill English at the famous Xerox Palo Alto Research Centre refined it in 1972 making graphical user interfaces (GUI's) possible.
Keyboard shortcuts might be faster, touch screens more intuitive, but moving the cursor on the screen with some other part of your body is still the most effective means to complete a lot of tasks.
The right mouse or mouse alternative can make all the difference for comfort, safety and efficiency.