Some people ask many questions and only accept answers. Never they give an up-vote. Meaning all the other participants to a question - who may either help or complement the accepted answer - get nothing.
That number is relative to the person activity - and should not always be displayed. But I think it is relevant in many cases (like
accept rate: 30%, upvotes: 0 where you know it is unlikely you'll get any rewarding for your work time [besides the other members of course] unless you are the accepted answer).
edit based on comments
Of course a user with 38% accept rate may have been unlucky with the answerers. Since we are talking about likeness, when someone has 20% accept rate, and 0 upvote after asking 50 questions, there could be a problem. Well, he may have been very unlucky with the answers he got, but probability-wise the odds are more keen to indicate the user is a bit tight in terms of offering recognition.