Pfft, there's other uses for it. Such as signing into accounts one time on other people's computers.

I personally use it all the time, for everything I don’t want to show up in an autocomplete context. I started doing this probably 8 years ago after I got annoyed Google would auto suggest misspellings I had previously made. I think they’re much better about this these days but at this point it’s an instinct for pretty much every single one off Google query.

That, in fact, is what it's often called within Google, I can testify.

How about "keep your spouse from finding out you look at porn" mode? Because that's what it's for.