When humans took the initiative to do something that they did not want to do, they definitely hoped for a reward.
Food and water were necessary for a human to live. Hobbies and interests were things that humans did to bring joy to their lives. Working and starting a business earned material possessions while getting married and having kids were to reproduce.
In other words, it was impossible for there to be any behavior in the world with no motives.
If one could not understand something at first, one would find out the reason for that behavior as soon as one turned around to look at the person's motive. Even for those whose minds worked in strange ways, the most one could say was that they were after something different than the rest. Therefore, Ye Shuang had been feeling that the girl's behavior was out of the ordinary since she was captured.