How come if youre a girl who experiments sexually with another girl...?

...youre just experimenting but if youre a guy who experiments with another guy youre gay. Idk i personally dont have a prob with two straight girls havin a little fun sexually once but if two straight guys did that id consider it a little weird and pretty gay. I feel like a lot of society has the same viewpoint. Am I wrong? (Im not a homophobe) just wondering why that is perception.