It might also be for comfort. If the son is wearing warm and soft clothes, mom could find it cozy to sit on his lap. Also, if the son doesn't mind and they have a very close relationship, it could be a way for them to bond during the long drive.
One possible reason could be that there is not enough space in the vehicle. Maybe there are a lot of bags or other items taking up the seats, so mom has to sit on son's lap as a last resort.
In some cases, it can be appropriate. If they are in a situation where there are no other options due to space constraints and it's a family - only environment, it may be okay. For example, if they are in a small camper van and all the seats are occupied with necessary items.
Well, generally speaking, it's not proper. We should uphold certain social and family norms. Mom and son are family members, but this kind of overly intimate physical contact like sitting on the lap might make both of them feel uncomfortable in a way, and it also doesn't conform to the common sense of propriety in family relationships. There could be other options like sharing a seat cushion or rearranging the seating in the vehicle to make the long drive more comfortable without this kind of inappropriate behavior.
It might be part of a creative play. For example, if they were acting out a story or a scene from a fairy tale where mom was playing a character that needed to be on the 'lap - horse' or something similar. This kind of play helps in strengthening the family relationship and creating shared memories.
Well, one possible plot could be that a young lesbian woman finally comes out to her mother. At first, the mother is shocked but then slowly begins to understand. They have a moment where they sit together, and the daughter sits on her mother's lap like she did when she was a child, signifying a new level of closeness and acceptance.
It could be due to a prophecy or a magical bond. Maybe there is a prophecy that says something about Hermione being in close physical proximity to Snape at a certain time. Or there is a magical bond that Snape discovers and he thinks that forcing her to sit on his lap is the only way to activate or understand this bond better, although these are all very strange and complex reasons within the realm of fanfiction.
Well, she could get hurt badly. If there's a sudden stop or an accident, there's no proper restraint for her. She might hit the dashboard or the windshield.
They could use a travel pillow to make the seating more comfortable. Or mom could sit next to son and share a blanket if it's cold.
Well, it could be about a complex relationship issue. Maybe there was a big fight between friends or family members, and it involves a lot of back - and - forth, misunderstandings, and different emotions.
One possible reason could be that the mom always wanted a daughter. Maybe she had dreams of doing girly things with a girl like shopping for dresses or having tea parties. Another reason might be that she has some unfulfilled desires from her own childhood related to femininity and is projecting them onto her son.
Maybe in a fashion - related story, the mom is helping her son with a school play or a costume event where stockings are part of the outfit.