To get back to the original question, why would it be of any benefit to know the growing conditions...
Perhaps it's the same reason winos like to know what is happening in Bordeaux. When you get your lafite rothschild, you have a sense of expectation, especially if you've been drinking it for the last few years. I just happen to love a few coffees we bring in as much as some people love LR, and I want to know everything about this coffee. Did it sit on the tree too long, what were the patio conditions (if applicable), etc I'm considering making a trip to El Salvador very soon, depending on if the samples I get tomorrow are what I am hoping for, because I'd like to use it for competition. Such has been my approach to coffee from day one - dive in, learn as much as possible, experience as much as possible and prepare to learn things you did not expect (aka: be surprised).
Likewise, for some Oromia coffees last year (esp in ours), they had a problem with ferment and it reflected on the cup.
Additionally, our co-op in Kenya had a poor year, and we ended up selling the coffee on the market (until New Orleans flooded) rather than roasting it ourselves. As it turned out the samples they cupped were not representative of the lots the roaster's group purchased.
Yes, you could know the weather conditions at origin, and it could not mean a damn thing, but in a total system of quality, weather is vitally important. As is knowing how your roaster develops the roast profile of his coffee. Is he or she developing those branch amino reactions? If I don't know, I'm going to get on the phone and chat with him or her, because it matters. I'm not a zen barista, but I am the person responsible for the product at the end of the line (and responsible for the work of my co-baristas). Thus, I need to be in close communication with the people at the other points of the chain.
Rob, did you ask Alistair why he went to Africa? Certainly, he doesn't buy green coffee, nor does he roast (that I know of). But it was obviously important for Alistair to go. For similar reasons, I want to know what is happening at origin. If nothing else, knowing the growing conditions makes the changes in flavour year to year more profound.
And lastly, I've been receiving both green and roasted samples for the past few weeks from my roaster of different coffees to play around with as espresso. I'm currently espresso geek number one as far as his customers go, and he values my feedback.
I hope this suffices as an adequate answer. It seems pretty obvious to me, but perhaps not to others. I couldn't see how I could do what I do and be apathetic to things like annual growing conditions, among other things. I couldn't imagine approaching coffee any other way.