It makes no sense, so why do people do it? Because society demands that apology, and rewards you for making it. In a Harvard Business School study, researchers sent participants into a crowded train station during a deluge and tasked them with bumming cellphones off of strangers. The participants were instructed to randomly either a) ask the stranger to use their cellphone or b) apologize about the bad weather first, and then ask to use their phone.
When simply asked to hand over their phone, the strangers were about as likely to do so as they were to push the participant into the path of a moving train. After hearing the superfluous apology first, on the other hand, the strangers felt an almost hypnotic urge to toss their phone to a possible identity thief in a crowded train station.
The series of experiments revealed that giving that unnecessary apology increases trust levels -- even though what you're doing is kind of dishonest, since you're getting sympathy for admitting to a mistake you didn't make. It's like humans are so eager to have someone to blame that you can immediately get on everyone's good side by becoming the apologetic public relations person for the universe:
"On behalf of the infinitely complex, uncontrollable cosmic forces that brought you today's weather, I apologize."