Why do contour interval on a topographic map of a mountainous area usually large?

Contour intervals on a topographic map of a mountainous area are usually large to effectively represent the significant elevation changes over relatively short horizontal distances. This helps to avoid overcrowding of contour lines, making the map easier to read and interpret. Larger intervals also allow for a clearer depiction of the terrain's steepness and major features, which is particularly important in rugged landscapes. Additionally, using larger intervals can help highlight important elevation differences that are relevant for navigation and understanding the landscape.