In traditional Chinese culture, the expression of affection is often more reserved and subtle than in many Western cultures. While this is changing with younger generations, the cultural context for kissing remains distinct.
Public vs. Private: A 吻 (wěn) is considered a very private and intimate act. Unlike in Europe or North America where couples might kiss openly in public, public displays of affection (PDA) like passionate kissing are still relatively uncommon in many parts of China and can be seen as inappropriate, especially by older people. A hug or holding hands is far more common.
Comparison to Western “Kiss”: The English word “kiss” is a broad-strokes term. You can “kiss your mom goodbye,” “kiss a baby's forehead,” or “kiss your partner.” In Chinese, these actions require different words. 吻 (wěn) is reserved almost exclusively for the romantic, on-the-lips kiss. For familial affection, the word 亲 (qīn) is much more appropriate (e.g., 亲一下脸颊 - qīn yīxià liǎnjiá - to give a peck on the cheek). Using 吻 (wěn) to describe kissing a family member would sound overly dramatic and slightly strange.
Related Values: This reservation stems from traditional values emphasizing modesty (含蓄 - hánxù) and saving deeply personal emotional expressions for private settings.