That's because the girl and your father-in-law don't live together. The son and daughter-in-law are together all day, but they feel bored. Of course, he thinks it's good for girls to buy something from time to time, but his son does it every day and he feels used to it. No matter what he says, just do what you should do, as long as you have a clear conscience and treat everything you encounter in life with a normal heart.