Why do some men do this lol?

Why do some guys only want to have sex with you (or are not ready to define the relationship) yet dont want you hanging out with other guys? I understand not having sex with anyone else, but even hanging out with them/going on a date?

Like unless we are officially dating, boyfriend and girlfriend, I dont know why I'm not allowed to go on dates if you're not claiming me?? Anyone else been through this??

He said "I didnt realize you would be looking elsewhere." DUDE. We are not dating!!! I didnt even think he would care!