The situation you describe can be quite confusing and frustrating for both parties involved. There could be several reasons why some guys say they are not looking for anything serious but then get upset when the girl wants something casual instead of serious:
Mixed signals: Sometimes, people give mixed signals or communicate their desires unclearly. They may not be sure about what they want, leading to inconsistency in their actions and feelings.
Fear of commitment: Some guys might genuinely believe they are not ready for a serious relationship, but when they see the girl they are interested in seeking something casual, they might feel a sense of loss or jealousy. This can stem from a fear of commitment or a desire for exclusivity without wanting the responsibilities of a committed relationship.
Ego and possessiveness: Some individuals may feel possessive about the person they are interested in, even if they don't want a serious relationship themselves. When they see that person seeking casual relationships with others, it can bruise their ego and make them react with anger.
Emotional attachment: Even if someone claims they are not looking for anything serious, they may develop feelings for the other person over time. When they realize that the other person doesn't share the same feelings or commitment level, it can lead to frustration and anger.
Social pressure: Society often places expectations on individuals to be in committed relationships. When someone feels like they "should" be in a serious relationship, they might claim they want something casual, but in reality, they may still feel the pressure to seek something more significant.
Desire for control: In some cases, a person may want to have control over the relationship dynamics. By initially claiming they want something casual, they might believe they can set the rules and boundaries. When the other person also seeks something casual, it can upset this perceived control.
Communication breakdown: Miscommunication and misunderstanding can play a significant role in these situations. Different people may interpret "casual" or "serious" differently, leading to conflicts and emotional reactions.
It's essential to remember that individuals are unique, and their motivations and reactions can vary widely. In such situations, open and honest communication is crucial to avoid misunderstandings and hurt feelings. Both parties should discuss their expectations and intentions early on to ensure they are on the same page. If there's a disconnect in what each person wants, it may be best to reevaluate the compatibility of the relationship.