They think there are the following points:
The first point is to be afraid. Some people may not understand this feeling, but it is our nature to be afraid of people who are stronger than ourselves. Women can't help but feel scared when they see muscular men, even after two people are together, so girls are reluctant to find such boys.
The second point is that muscular boys are afraid of being violent towards themselves. In fact, this is just a girl's own imagination. We have no evidence to prove that muscular boys are prone to violence. In fact, violent tendencies have nothing to do with a boy's appearance. What really matters is a person's character.
Third, girls will find such boys difficult to get along with. Indeed, a muscular man is very strict with himself. They may go to the gym to exercise every day, while girls generally like to go shopping or stay at home. They are worried that after two people are together, boys will ask themselves to exercise. In fact, most boys just have such requirements for themselves. Their request for the other half is actually very simple, as long as you are in good health.