@Alex To be fair, it does say "skip to the bottom" at the top.
But I can imagine instances in which I read a question, have some thoughts about how I would answer it, and one or two points that I think would be indispensable in a good answer, then see an answer that contains the indispensable point, and immediately +1 it in my mind. If it's a point I'm really excited about that could translate into a physical +1 even before I read the rest of it. Of course if I change my mind later I just reverse my vote.
@WAF Yes and no (to your last point). You only have a short amount of time (five minutes? I forget) to reverse or even undo a vote, unless the post's been edited in the interim.
@Alex You can click "edit" on the post to see the source. There's no button for it. To make a reference in the text, I write <sup>1</sup>. At the bottom, I add --- for a line and then <sup>1. Footnote text ...</sup> for each footnote
sup is the HTML tag for superscript, which means small print, set half a line above the normal base line.
I don't know if you're used to HTML, but in HTML, you format text by putting a tag that specifies the format before the text and a tag that specifies ending the format (with a /) after the text.
I add a few spaces at the end of each footnote so that I can put them on successive lines in the source, and they end up rendered on successive lines, rather than all on one line.