It's indecent to brag about your sexual conquests.
Andrew is at work talking to Tom when Tom asks him in front of everyone how his night was.
Andrew wants to tell everyone about his night.
Andrew tells the group that he met a nice young lady and that he generally had a great night.
Andrew tells the group that he bagged the hottest chick ever and that he took her home for a one night stand.
The group is delighted to hear Andrew had a good time the night before.
The group is disgusted to visualize Andrew doing these things and wonder why he feels the need to tell anyone.