Most people have no idea because most people do not make any decisions based on interest rates. It just isn't material in their decisions.

If you tell me next thursday it will be rainy, I'll remember to bring my umbrella. But tell me interest rates go up and it doesn't really affect my decision to get a mortgage or not. Either, I've found the perfect house with a mortgage that is affordable (in which case I sign) or I haven't. At no point does knowledge of the interest rate make any difference in my decision.

I think the real reason its reported as its a nice round figure that is a barometer of sorts on the economy. Great for providing some meat around a story. Bonus points for sounding like the sorts of thing smart and respectable people would want to know. I'd be interested in your opinion about why changes in interest rates are so important for the press.