He doesn't step in front of her. When mounting a stairway, the guy stepped behind her since women wore long gowns and may trip on them. Tumbling down a flight of stairs is not an appropriate way to finish a date. Today, the guy adheres to this etiquette norm since she may be wearing high heels or a lengthy gown. He wants to make sure she isn't injured. The reason why a gentleman doesn't walk ahead of a lady is because it's polite to let her enter first. In olden days, when men went out, they didn't know if it was safe for women to go out so they made sure that they entered first. This is still true today in some countries where women don't have equal rights. For example, in Saudi Arabia, Iran, and some other Arab countries, women are not allowed to drive. So, they need someone to walk ahead and open doors for them. Also, in some countries, it is customary for men to give women a little distance (about 3 feet) in public places like parks. This is so they can get out of the way should the woman want to pass without being touched. Finally, in some cultures, it is considered very rude for a man to walk ahead of a woman. This is especially true if the woman is very tall or has long hair.