When should mechanical/physical controls be eschewed in favor of touch-based controls? When:
- You want to change the functions, layout, number, size, etc., of the control buttons [like in smartphones].
- When you want to protect the controls from dust, water, etc.
- When you want to eliminate/reduce the effort to push the mechanical/physical buttons.
Some automobile manufacturers [e.g., Honda] have introduced touch-based controls in some cars [e.g., Honda in City]. I think this is a ridiculous and backward step. Why? Because:
- The functions of these touch-based buttons remain fixed. They don't need to be changed.
- There's no extra need to protect the controls from dust/water.
- There's no compelling need to reduce physical effort to push physical buttons.
- A user must look at the touch based buttons in order to operate them [to correctly place his fingertip on the correct button], unlike physical buttons/controls that can be operated quickly and correctly without requiring us to look directly at them.
- Many times, touch-based controls accidentally get pressed, leading to undesired and unintended operations. Over time, a user subconsciously starts being extra careful, creating unnecessary extra mental load.
- There's a certain kind of live feedback we get when we're, for example, rotating a knob to set the fan speed to the correct level. This feedback is quite satisfying and helps us to stop at precisely the most satisfactory point. This feedback is completely missing from touch-based controls.
- In a physical rotating knob, you can continuously vary the level of the setting that the knob controls, and feel/hear the changes in real-time, and stop at exactly the level that you deem fit. However, in a touch-based system, you need to repeatedly touch the button to move the setting in one direction, and in order to move it in another direction, you need to move to a second button and repeatedly touch it. This setup is far more cumbersome compared to a physical rotating knob where you neither need to repeatedly touch nor you need to shift between up and down buttons.
In summary, car manufacturers and other companies shouldn't mindlessly employ touch without giving thought to its need and usefulness according to circumstances. Touch should be employed where it's going to be genuinely useful.