What feature is not universal in old vehicles regarding turn signal switches?

Not all old vehicles have self-canceling turn signal switches. Self-canceling mechanisms are designed to automatically turn off the turn signal after the vehicle completes a turn or maneuver. While more modern vehicles commonly include this feature for convenience and safety, older vehicles often relied on manual operation. Drivers would need to remember to deactivate the turn signals themselves after completing a turn, as the absence of a self-canceling function was a design characteristic of many older models. This lack of uniformity in design is what distinguishes this feature from others, such as the operational status or the presence of manual indicators, which tend to be more consistent across various old vehicle designs.