We as geeks really need to stop underestimating people. It reflects poorly on us.
I have worked in tech support, so I have seen the way that many people use their computers.
While a few people do surf the web as you describe, their numbers are small. While it is true that most people do not see the benefit of changing browsers and therefore stick with the default, most of them can and do change their home page, most of them know what a bookmark, address bar and search box are, and most of them use google.
By the way, I have seen very few computers for the home that have a microsoft home page. In my experience the manufacturer sets it to their own page. It is only the corporate boxes that have MSN, as far as I have seen.
Funny side note, the time I told somebody to go to slashdot.org, he typed /..org in the address bar. After that I used google.