Just because your friends say they are 'doing it' doesn't mean they are. Thinking through all the implications of having sex can be a useful way of helping you arrive at a decision. There are lots of reasons why people don't want to have sex. You may feel that you are not ready emotionally. Being pushed into having sex could mean you regret it later on.
Some people have quite strong religious or cultural beliefs.
Other just want to wait. Some people call this decision to wait 'abstinence'. Some people decide that they do not want to start having sex until they are married or in a significant long-term relationship. Other people may decide that having sex isn't the right thing for them at this particular time. Later on they may meet a person who they want and feel ready to have sex with.