Why Are Americans Now Remaking Old Movies?

For the past two to three months the American movie adverts i've been seeing are based on old movies eg
                                  
                             LEGEND OF ZORO 

                             KING KONG

                              ROBIN HOOD

                             BATMAN BEGINS , and so much more.....
            What shall we then say: "Are American running out of Movies or what? Then why are they now acting Old films. Really, i don't know but anyone with a better idea can help me out.
Thanks. Please i await contributions

or maybe they feel that they have better technology and stuff now than the limited ones they had in the past to make the newer versions better than the old ones.

these movies they remake are usually classics too meaning : they live forever!! (maybe they don't want the stories to die?  )

Maybe they've just run out of fresh ideas.