Why would a guy your just sleeping with on a regular basis give you a spare key to his apartment?

A guy I’ve been sleeping with on a regular basis for just a few months. I guess you can call it a just having fun friends with benefit’s sort of thing. Lately he’s been talking about going out of town together & He told me he was going to give me a spare key to his apartment so I could come over whenever I wanted. Why would he do that? We’re not together like that nor are we even close friend wise so I’m alil confused on why I would qualify for a key to his apartment unless he liked me enough to make me more….
Why would a guy your just sleeping with on a regular basis give you a spare key to his apartment?
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