Many of the vectors Blackhole used (like Silverlight and older versions of Java) are no longer necessary for the modern web.
Amateur hackers attempting to repurpose old code for new, albeit often ineffective, campaigns. The Risks of Downloading Legacy Exploit Kits blackhole exploit kit download
Possessing or distributing exploit kits can fall under various computer misuse acts depending on your jurisdiction. Many of the vectors Blackhole used (like Silverlight
Many archived versions of the kit are bundled with "backdoors." If you attempt to install the kit, you are likely to become the victim of a more modern malware strain. albeit often ineffective
Individuals looking to set up "malware labs" to practice defensive techniques in a controlled environment.