There could be several reasons why some people don't smile back when you smile at them first:
Personality and mood: Everyone has their unique personality traits and moods. Some individuals might naturally be more reserved or introverted, and they might not feel comfortable smiling at strangers or in unfamiliar situations.
Social norms and cultural differences: In some cultures or social settings, smiling at strangers or people you don't know well might not be the norm. Some individuals might interpret a smile as overly familiar or insincere, leading them not to smile back.
Distracted or preoccupied: The person you smiled at might be preoccupied with their thoughts or concerns, and they might not have noticed your smile or registered it in that moment.
Negative experiences: Some people might have had negative experiences in the past that make them wary of interacting with strangers or smiling back at unfamiliar faces.
Social anxiety: Individuals with social anxiety may find it challenging to respond to social cues like smiles, even if they appreciate the gesture.
Cultural background: In certain cultures, maintaining a neutral facial expression is considered more respectful or appropriate, and smiling openly at strangers might not be customary.
Misinterpretation: In some cases, the other person might have misinterpreted your facial expression as something other than a smile, leading to a lack of reciprocation.
Personal circumstances: The person you smiled at might be going through a tough time or dealing with personal issues, making it difficult for them to respond positively at that moment.
It's essential to remember that everyone is different, and there could be numerous reasons behind someone not smiling back. It's not necessarily a reflection of your actions or your smile's impact. Being understanding, empathetic, and respecting others' boundaries is crucial in all social interactions. If someone doesn't smile back, it's okay; just continue to spread positivity and kindness whenever you can. Some people might appreciate your smiles even if they don't reciprocate, and your actions can still have a positive influence on their day, even if it's not immediately evident.