because the sinking of the Titanic has proved to hold the interest of the world for nearly 90 years after that fateful night in April 1912.
I don't know if I can say I've seen "all" the Titanic movies, but I have seen Leonardo Di Caprion's version, Catherine Zita-Jones' version, Clifton Webb's version, and this one, which was the first one I ever saw, years ago, as a little child. Hands down, this British version is the best.
It's not that the others are stinkers; in fact, that would lessen the victory. After all, Leonardo's has some great special effects, Catherine was a pretty passenger, and Clifton Webb handled disaster very well. But this one has the hallmark of accuracy to it. When you've finished watching it, you KNOW the story of the Titanic well enough to perpetuate its memory to your own children's children. It captures the despair of the passengers who realize what's really happening, and faithfully recounts the different vignettes of self-sacrifice which characterize this tragedy in particular. Unlike the other three movies, "A Night to Remember" doesn't have to invent people for you to identify with; the real stories are far better than any invention and far more poignant.
Watch the others for entertainment, but watch "A Night to Remember" for edification.