The human mind isn't wired for facts and figures; we're wired for stories. That could be why we are so often treated to anecdotes about so and so's friend/cousin/ neighbor who adopted and then got pregnant/tried x,y, or z and then got pregnant, etc because a) most people don't know the facts and figures and/or b) what sticks with them is the story, even if it is an anomaly rather than the rule.
Most of us have seen this graph (top of the page) focusing on NaPro Technology's success rates for various underlying causes of infertility. But let's face it, a graph and numbers aren't the easiest things to connect with on a visceral level. It's the stories that hit us hard; the stories that we deeply connect to. In our little corner of the blogosphere, we have success stories (like Katie, JBTC, Sarah, and others), hard cases (like Amy, Jelly Belly, and Kat, amongst others; in this case, I am using "hard cases" to describe those who have tried extensively, in some cases to the limits of what is available medically), and those of us who are somewhere in the middle, still exploring options and trying to identify the underlying problems.
I would argue that those of us in the middle need both the success stories, to give us hope, and the hard cases, to keep us grounded. Depending on your personality and where you are in journey, you may connect more closely to either the success stories or the hard cases. Both because of my age and my temperament, I more strongly connect to the hard cases rather than the success stories. Yes, I know that NaPro has helped even women in their 40s conceive, but I am still enough of a scientist to acknowledge that the probability decreases with increasing age. (It probably doesn't help that many of the success stories that I am familiar with are women a decade or more younger than I.)
That may also tie into my reasons for strongly preferring the term "infertile" to "subfertile." To my mind, "subfertile" suggests that if you just try long enough, do enough medically, you will succeed. According to the facts and figures, most couples, including those with infertility, will eventually succeed (past performance is not necessarily indicative of future results, as all the mutual fund commercials say). And right now predicting who will eventually be able to succeed or what a couple's odds are is mostly educated guesswork. Infertility has a concrete clinical definition, which is part of why I prefer it, though there's nothing wrong with preferring subfertile. (I'd be curious to see if those who prefer subfertile are more likely to feel a stronger connection to the success stories than those who prefer the term infertile, but that psychology experiment isn't one I plan to run.)
We need both the examples and reasons to hope and the awareness that we might never succeed. Or, as Dolly puts it, "something lifting me up, something holding me down."