The use of kilometers or miles on the odometers of bikes, as well as other vehicles, is primarily determined by the region or country in which the bike is intended to be used. The choice of measurement system is based on historical conventions and regional preferences for measuring distances.
In many countries outside of the United States, the metric system, which includes kilometers as the unit of measurement for distance, is the standard. These countries typically use the metric system for various applications, including transportation, and therefore bikes manufactured and sold in those regions have odometers that display kilometers.
On the other hand, the United States primarily uses the customary system, which includes miles as the unit of measurement for distance. Therefore, bikes sold and used in the United States generally have odometers that display miles.
It's worth noting that while there is a general trend towards the use of metric units worldwide, the transition can be gradual, and different countries may still adhere to their respective systems. This can lead to variations in the units displayed on the odometers of older bikes, depending on the country of origin or the intended market.
In summary, the use of kilometers or miles on the odometers of bikes is determined by regional conventions and preferences for measuring distances, with different countries adopting different measurement systems as their standard.