Your IP makes incognito relatively pointless, and that's before you get into various clever forms of browser finger printing. If you want privacy you need to use TOR. Incognito should be treated as a convenient way to run without cookies / to log out of sites temporarily. It's also nice for sites such as YouTube as they'll pretend to not know who you are so you can get recommendations related to what you're currently watching instead of just constantly recommending everything you've recently (or not so recently...) watched instead.