I have not had the time to look into the details of this very important 'conundrum, but from the few articles I have read, the reason is that the two particles are manufactured into one of exactly two quantum states at birth. When they are far apart, they are still in such a quantum state and our observation of one of them does not actually involve information traveling faster than light in any way that we could take advantage of for FTL signaling.
Suppose I took two colored balls, one red and one blue, and put them in sealed boxes, and gave one to you in New York, and took the other to San Francisco. Then I opened my box to see the red one. I would immediately KNOW that your's is blue, and these aren't even quantum systems! Seemingly, information or SOMETHING has traveled faster than light, but what is it? What is the velocity of 'ignorance' being replaced by 'knowledge'?