Bitcoin is being used by people, human. And some of these people are criminals, some are good people (like me). So, stop worrying about it and just accept it. Hey, it's a currency after all. Who doesn't use money huh? Come on.
The BTC was being created for everyone. The problem is, it can be used by an anonymous person the reason why it is hard to trace if who is the current user of every account. Some people took advantage of using it by illegal transactions. Since bitcoin is free to used by everyone, then it is possible that criminals could also used it.