forgotten ID

so i forgot my work-badge today. for those who don't work in corporate office buildings, this badge is your ID/electronic passkey. I can't get into the office without one. fortunately, there is a lot of traffic in and out of the office and there are windows on the door which i wait in front of, so i don't normally have to wait more than 2 minutes for someone to come by and let me back in from leaving the office to use the restroom. Happens to everyone at some point, you forget your badge and are slightly inconvenienced.

For some reason, this is incredibly funny to people at my office. Every time i've been waiting at the door, whoever lets me in just starts laughing. I politely say thank you, and walk to my desk. why is this so funny? i'm not offended or hurt in the slightest by the amusement at my forgetfulness, but this is an incredibly puzzling phenomenon.