Why does Word screw up URLs?

I’ve been using Word for a long time – more than 20 years!  I recently stumbled upon a “feature” which has caused me a bit of grief over the years and how to turn it off!

This is described in a Microsoft article, on using absolute hyperlinks.

The thing is that the option to use an automatic relative hyperlink is selected by default.  So unless you un-select it those lovingly crafted absolute links of yours along the lines of http://mydomain/webthingy/index.html will get turned to files:///c:users/dopeyworduser/appdata/webthingy/index.html when you save!

Perhaps someone could point out to me the benefit of having this defaulting to “on”?  I ask this as a long time “Dopey word User” who now knows better.