I agree I do think the ratio of views to responses is a bit dismal, and I try to help out whenever I can. I'm gonna really honest here, though. Lately I've become much more restrained in posting because out of every seven or so people I take time to post advice and/or encouragement for, maybe one person sticks around so it almost feels pointless. Granted, it doesn't take more than a few seconds to post a quick hello and welcome, but personally, wherever possible, I strive to make more sincere and substantive posts, so it doesn't feel so mindless and mechanical.
I'm not saying its completely futile but I think many posters are suffering this same "Greeter's Fatigue" I've gone through. Ultimately, the board retention rate is not something we can change or control, but I thought I'd just offer some insight into the situation.