Why do the front wheels not turn in unison?

The front wheels of a vehicle do not turn in unison because they need to accommodate the different turning radii required when navigating a curve. The inside wheel travels a shorter distance than the outside wheel, necessitating a differential steering mechanism, such as a rack and pinion system. This allows each wheel to rotate at different angles, improving control and stability while cornering. Additionally, this design helps to reduce tire wear and improve overall handling.