Well, it is not the problem with Bitcoin but the human involved. There are also cases whereby people buy and sell drugs or involve in any illegal activities using fiat.
You stated a fact , involvement of illegal activities in this platform is possible. Anonymity frature of Bitcoin is somehow welcoming this kind of activity due to its function that to require less personal information about a person who owns account here, it enables some people to steal and scam without any trace for them which leads us to be vulnerable to this.