My roommate doesn't want my boyfriend to come over?

Me and my boy friend just keep to ourselves when he comes over. We lock the door and he just stays in my room. We don't go to the other areas. We don't cook or create any mess. I'm not sure why then does my roommate have a problem with him coming over. I have another roommate and her boyfriend used to stay over all the time and they would even cook and dirty the kitchen. And they didn't complain to the other roommate but why is it in my case they complain?
My roommate doesn't want my boyfriend to come over?
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