Asking About Age: In many Western cultures, asking an adult's age, especially a woman's, can be considered impolite or invasive. In China, however, it's traditionally a much more common and neutral part of getting to know someone. It helps to establish seniority and understand one's position relative to others, which is important in a culture that values hierarchy and respect for elders. While younger, more Westernized urban populations might be more private, it's generally not a taboo topic among peers or when making new friends.
Comparison to Western Norms: Think of asking “你多大？” (Nǐ duō dà? - How old are you?) as being socially closer to asking “What do you do for a living?” in the West. It's a standard piece of information for building a social map of the person you're talking to. The intention is usually rooted in friendly curiosity and establishing rapport, not judgment.
Age and Respect: Age is directly linked to the Confucian value of respecting one's elders. Knowing someone's age helps you determine the appropriate level of politeness, which pronouns to use (like the formal 您 nín), and how to address them. Adding a 岁 to your life, especially during Chinese New Year (when everyone traditionally becomes one year older together), is a significant event. This is also linked to the tradition of “压岁钱” (yāsuìqián), the red envelope money given to children to ward off evil spirits associated with the passing of the year (岁).