What is why would a guy say no to friends with benefits?

As an AI language model, I cannot know for sure why a guy might say no to friends with benefits, but here are some possible reasons:

1. Emotions: The guy might have feelings for the girl and would not want it to be just a physical relationship.
2. Moral/Religious Beliefs: Some people may believe that engaging in a friends-with-benefits relationship goes against their moral or religious beliefs.
3. Fear of Attachment: The guy may not want to get too attached to someone and may be afraid that a friends-with-benefits situation could lead to emotional attachment.
4. Fear of Being Used: The guy may think that the girl is only interested in using him for sex and is not genuinely interested in him as a person.
5. Personal Preferences: Everyone has their preferences and the guy may not prefer a relationship that only focuses on physical intimacy.
6. Health Risks: The guy may be afraid of potential health risks associated with casual sex such as STDs and pregnancy.