In MSWord when you look at a table of contents you see the page number of a subject matter and you can use the "Go to" function. In eBook you can see the page number (updated as your font does) and scroll with the bar below to that particular page.
We can also ask why is this option available even in MSWord, but I don't really care about the answer, if it's possible in any document over PC or Mac I expect it to be available in eBooks as well. True, is nothing BUT luxury function.
That being said, I am not asking this for my own amusement, I am asking this because I am making an eBook for someone and they asked if that is possible. I couldn't care less if that function is there or not but when someone else is asking and you're working for them then... you post here I guess