I agree. However Cameron had a wider demographic in mind. What struck me (at the time the movie was in theatres) was that people of all ages and all backgrounds flocked to see it. Not everyone likes watching documentary style films. Ergo the fictional caracters for the younger generation were introduced. That seemed to draw a younger demographic. Older viewers were drawn by the factual parts of the movie. Cameron obviously had to balance the two aspects of the film (Fact and fiction) within the allowed feature length of 3hours and 15 minutes. It will be interesting to see the full director's version of the film just to see how many factual scenes were sacrificed in order to accomodate the fictional storyline. To my knowledge it was a hard attempt by Cameron to include these factual scenes in the theatrical release but studio executives over-rulled him.
I aggree that more factual aspects would have certainly enetrtained me. But many people have different tastes and I am also sure that many probably would have nodded off in the theatre had Cameron included too many factual scenes. Lord of the Rings (for example) is entertaining up to a point were the extended editions get rather boring when to much emphasis is made on mythology and detail (unless you are a true fan of course). One can't compare the two movies but the principle remains the same. If you include too much information, the audience will get bored. (especially after watching for 4 hours) I can't wait to see the director's cut of Titanic though. If you are a fact junkie like me you might enjoy a 4 hour rendition of Titanic laden with facts and history. Fictional finatics might fall asleep though...