One of the most difficult things about getting sober is that we sometimes need to change the people we spend time with or the places we go. People who do not respect your wish to be sober are not true friends to be quite frank. You may need to stop hanging around with them. As to the question of "why" they act as they do or say what they say, you will most likely never know. But if they continue to try and get you to drink even after you tell them you don't want to, i'd strongly suggest finding other people to hang around with.