Why does the contestants on American Idol sing such rubbish songs,and they murdered the Beatles music.?

As a Brit,in my 60s.I remember them well.These girls and boys had never heard them,I expect.Their music is very hard for one person to sing,especially a woman. Is it something to do with copywrite that they always seem to sing such unknown music? I think David will win.I cant pronounce his name,but will try.Where does Archeloto come from.He is a nice looking boy,but does he have slightly almond eyes? Can he have in his past have had something to do with the Aztec indians,in South America? Thats how it sounds to me..From my research I can see the final winner has never been in the bottom three.Jason Castro,perhaps the 2nd best was in the bottom 3 two weeks ago.