The Illusion of Privacy
Incognito mode: for when you want to browse privately but also want your browser to judge you. "Oh, looking up 'how to tell if a cat loves you' in incognito? Very subtle."
The government probably still knows. Your ISP definitely knows. Your router knows. The only one who doesn't know is YOU about what you just looked at because you forgot.
The Real Use
Actually, I use incognito to get around paywalls. And to hide my Amazon history from my wife. And to look up weird medical symptoms without them appearing in my search history. Totally normal stuff.