Attribution
In the news we often see attacks traced back to government-backed hacking groups ("APTs"), because they repeatedly use the same tools, leave the same footprints, and even use the same infrastructure (domains, emails, etc). They're negligent because they can hack without legal consequences.
I didn't want to make the police's work any easier by relating my hack of Hacking Team with other hacks I've done or with names I use in my day-to-day work as a blackhat hacker. So, I used new servers and domain names, registered with new emails, and payed for with new bitcoin addresses. Also, I only used tools that are publicly available, or things that I wrote specifically for this attack, and I changed my way of doing some things to not leave my usual forensic footprint.