How is That Still Interesting?

Okay, so here is something I really do not get.

Take a pervasive issue like global warming, or healthcare, or the economy. At the start of the issue (or, if it's been around that long, new news-following generation), people are all, oh man!! But, within a few weeks, interest fatigue means that they hardly pay attention to the latest headlines on the issue.

Now, take a person. Say, a celebrity. They do something bad, it's everywhere. They do something bad three months later, it's everywhere. Six months, a year, ten years--people are still interested. And not just at home, but comics talk about it, it's a hot topic online....

Why does it seem that interest level in famous people accumulates, whereas for important issues that might actually have a bearing on one's lives, it decumulates (yes, I made that up, and yes, I know that there are plenty of real words out there)?

My guesses:
a) Reality is scary
b) People are idiots
c) We've evolved to focus more on people than things or abstractions

Of course, only c) has a chance of changing at all. They've found a rise in myopia since computers and not working outside became prevalent; makes sense, do we really need distance vision anymore? At the same time, our brains do need to start evolving to see abstractions as important.