First of all, I don't think that's a fair assessment. There are plenty of people who do in fact care very much about Africa and its people. UNICEF, Doctors Without Borders, CARE, and just about every AIDS group you can think of is involved over in Africa quite a lot.
If you mean "Why isn't Africa a higher priority for most of the world's goverments?" then I think you are hitting nearer the mark.
I'm no expert on Africa, but I think there's a couple of reasons why it doesn't peg a bit higher on the attention-o-meter insofar as the US is concerned.
Hitherto, Africa hasn't had a whole lot to offer us. Sounds harsh, I know, but it's the truth. We are forced to deal with the Middle East because they are a big energy source, but if the oil wasn't there we wouldn't be either. African oil is starting to become a market player now too, so some of our attention may be shifting towards that region.
The other main reason is the perception that Africa is a continent filled with people who simply cannot get their collective sh*t together. It's brimming with petty dictatorships, bloody coups, transient goverments, unending civil wars and ethnic violence. In the international arena there just isn't anyone reliable to deal with on a nation-to-nation level. Our news stories have left me at least with the view that Africa is a limitless sinkhole into which all the world's largesse could be poured without doing much more than fattening up a corrupt few at the top and financing more armies to fight in the wars and/or commit the heinous genocides we read about all too often.
Do the African people suffer? Of course they do! Most of those organizations I listed at the top are all about addressing the suffering on the individual's level. But until Africa starts to produce more responsible goverments, not too much will ever be done geopolitically to help them.