1. Clean up social networks: After graduation, many people may clean up their social networks and delete people they think they are no longer in contact with in order to manage their social life more effectively. This may include removing you from their list of contacts or friends.

2. Privacy and security considerations: After graduation, people may pay more attention to protecting their privacy and security, and may delete or hack some people they no longer want to contact, so as to reduce potential social interference or avoid potential troubles.

3. Emotional changes: During your college years, you may have established a certain degree of friendship or contact. However, after graduation, people's life and emotional state may change, and they may be alienated from their former friends or classmates, which may lead them to pull you off their social media.

4. Unconscious negligence: Sometimes, people may unconsciously ignore some people without realizing that doing so may make others feel neglected or excluded. This may be because they are too busy with their new life and new social circle to notice your existence.

5. Other reasons: Everyone's situation and motivation are unique. There may be some specific reasons, such as some kind of conflict or misunderstanding between you, or their own personal problems or emotional state.

Whatever the reason, it is important to accept and respect other people's decisions. Although this may make you feel confused or uncomfortable, everyone's life and relationship will change, which is also a part of life.