Boys may resent being someone else's bestie for many reasons, which may include gender identity, social pressure, and personal preference. Some boys may believe that being friends with women is inconsistent with their gender identity. In traditional gender role concepts, men are generally expected to be friends with other men, while women are expected to be friends with other women. Therefore, for some boys, being a girl's best friend is not the image they want.

Social pressure may also make boys resent being someone else's best friend. In some social circles, friendships with people of the opposite sex are considered problematic, and this perception can lead to discrimination and ostracism for boys. This is particularly common in adolescence, as this age group tends to be particularly sensitive to peer relationships.

Personal preference is also a factor that affects boys’ aversion to becoming someone else’s bestie. Everyone has their likes and dislikes, and some guys may be more inclined to form strong friendships with other men. This doesn’t necessarily mean that they disrespect women or hold stereotypes, it’s just that they’d rather be around people who have similar interests and hobbies to themselves.

The reasons why boys dislike being someone else’s best friend may also include sexual orientation and gender identity. In some cases, boys may be afraid of being identified as gay or transgender, and this psychological pressure can also lead to their reluctance to make friends with girls and become their best friends.

There are many reasons why boys dislike being someone else’s bestie, involving gender identity, social pressure, personal preference, sexual orientation and gender identity. However, we should respect everyone's choices and preferences, and should not view friendship relationships too rigidly in terms of men and women being separated. In this diverse society, we should encourage and support the establishment of true friendships between different genders.