Why the FUCK would a male agree to an open relationship?

non-exclusive plates are different than open-relationship. I got a girls number and thought she was pretty cute. Right as we are texting she just told me "if we are going to meet up, you should know I am in an open relationship"

Wtf? Why would a male agree to this? He just loses out completely. Women can fuck whenever. Men have to work for it. Its an inherent disadvantage?