Why are tom and lily find when they return Mrs hatching handbag?

Tom and Lily are fined for returning Mrs. Hatching's handbag because they took it without her permission, which is considered theft, even if their intentions were good. The fine serves as a consequence for their actions, emphasizing the importance of respecting others' property. Additionally, the situation highlights the complexities of morality and legality, showcasing how good intentions can sometimes lead to unintended consequences.