We know that boys and girls can both do lots of the same things - boys and girls are both smart, sporty, creative, adventurous, kind etc. So we know that in reality boys are not more than girls, or better than girls. I am interpreting your question as, “even though boys and girls can do lots of the same things equally as well, why are girls thought to be less than boys?”
This is known as gender inequality, and it started many years ago when things were very different in society. To give you a very brief snapshot; historically, females were considered the nurturers, the bearers of children, and the ‘homemakers’, and men were the providers, considered the head of the family. Over time as technology and science evolved, so did society and gender roles. Along with the advancements, such as the contraception pill for women, childcare, and education, women entered the workforce and began challenging traditional gender roles which meant that men were doing things that only women used to do, and women were doing things that only men used to do.
Our society today recognises that girls and boys are both very capable and can do lots of the same things equally as well, however because our society had made decisions about how girls and boys should be, for example “boys are more sporty and never cry” and “girls should wear dresses and always present themselves nicely” sometimes boys and girls are not considered equal, even though they are. When this happens sometimes boys and girls are not given the same opportunities.
It's important that you know that as a girl, or a boy you should be given the same opportunities and that you should not be left out or discriminated against because you are a girl/boy. If you are in this situation, its important you talk to your parents or teachers about it to see if you can be included in the activity.
We need to be careful here because this is almost a stereotype! Perhaps the boys you know play more video games than girls, but in some schools/ towns maybe girls play more video games than boys? We really don’t know.
This is because of stereotypes! A stereotype is an overly simple belief about a particular group of people and is often negative. By stereotyping we assume that a person is, thinks, or acts like all members of a certain group. For example, a stereotype is that all girls like dressing up and wearing makeup and that all boys like sport. They make us ignore differences between individuals and think things about people that might not be true. They also make us believe that people should act in certain ways which can make us treat others badly because they don’t ‘fit’ a particular stereotype. So, we need to be really careful when we make assumptions about other people just because they are a girl, a boy, short, tall, skinny, overweight, living with a disability, have different cultural backgrounds to ourselves or any other factor.
Sometimes it can be easier for people to see girls doing “boy things” because we’re used to girls being “tom-boys” but it’s not as accepted for guys to do “girl things”. Hobbies and interests don’t belong to genders, and so it’s important for you to do whatever passion you have, no matter whether people think it’s meant for another gender. Do whatever makes you happy.