I believe Jobs needs this. His company has blossomed so much over the past 5 years and he has been working non stop on getting all of these products released. With a few months off we should see him back at the helm.
The reason that people care about Apple's stock, is because many have their life savings tied up with Apple. There are many funds that are very heavy on Apple stock which are where a lot of folk's retirement is coming from.
Now most people are as sympathetic as can be for someone that they do not know and have never met, but fact remains Jobs is the focal point for a very large company and has been pretty quiet about the health issues. He would probably do well to announce a transition plan in the event that he is unable to continue running the company so it won't be a huge hit to the market when/if it happens. I understand his desire for privacy, but it's simply the price you pay when running a mega corporation where the CEO is as visable as the product that you sell.