Ask HN: 12 years without antivirus software

I have been computing daily without any antivirus installed on my PC for over 12 years. My PC never got any virus, malware, adware, or anything that can ruin my life. I follow strict rules to avoid getting infected, e.g. never let anyone access my pc, nobody is allowed to visit untrusted sites, not allowed to connect any external device. NSA got hacked, CIA got hacked. How it happens? Why experts get hacked?