Excerpt from this article:
Physical interfaces are crucial for automotive usability. Operations rely on a simple glance or muscle memory. Touchscreens, by contrast, force drivers to look. Because buttons are not fixed to specific locations, screens inhibit muscle memory and findability. Touchscreens compete for attention with the driving process, adding to the dangers of distracted driving.
Serious interfaces — those that are repeatedly used by a knowledgeable professional and/or in potentially hazardous situations, should not be touchscreen based. If a touchscreen must be used, it should be embedded alongside a set of fixed, physical buttons that support muscle memory and single actions.
What’s happening to in-car interfaces now? Five years later, we’re seeing some car models stick to physical buttons and dials, and that’s a great relief.