The problem is that it is hard to tell (looking at the data en-masse) if 1 answer is enough. If every question was solved with just one answer, I'd consider that good (although a second/third perspective is obviously very welcome). So perhaps to understand the data we'd need to separate out the questions which are ticked, or have no tick but a highly-rated answer (most likely: the right answer, but to a drive-by user who didn't mark it complete and is now deleted through age).
You might also need to exclude CW questions, as these tend to get more than average replies; and we used to get a lot more of the "what is your favorite *" questions. I wonder if this is also skewing the answers? Most "real" questions get (from what I see) < 5 replies, in part because we've actually got some clever people on the site who have given the right answer already.
So an average of, what, 2.5 answers/question doesn't concern me.