Which benefits everyone if the problem is a simple thing you can resolve by helping them directly. Support is also part of the experience, and good customer support should factor into the review as well.
I can see how you'd see this as providing a positive bias, but I see it more like getting a chance to see if you can't help the customer out before they give up on your app. It also reminds the customer that there are people on the other end - so even if the issue can't be resolved, and you still get a one-star rating, the level of vitriol seems likely to be reduced - something all too easy to forget when angry-reviewing.
Of course if they just take the feedback and dump it, that's a different story - but again, I would think anyone with that experience would still leave the negative review.
TL;DR - too many downloaders use negative reviews as a combination support request and cudgel. I think this is a reasonable defense against that.
