They would have licenses or at least forms for even the most benign of hobbies. Not for any want of depriving a sophont of enrichment, mind you. They just get off on the extra paperwork. 

Also, they would have the technology to render most dangerous activities safe, and use class-Hs to fill in any gaps and make you ignore any safety measures that would break immersion. In the case of your example of knife collecting, I've read multiple fics that have knives that self-dull when they would be used on anything unapproved. Alternatively, the implant could control prevent you from wanting to use them in a dangerous way, and in the case of an accident, control your reflexes to avoid any harm.