WHY? do no composers today write music like MOZART and BEETHOVEN...?

I think it's because composers are well aware that "it's all been done before" by the best geniuses and musical masters. To try to write something akin to Mozart or Beethoven would almost certainly lead to being compared and not coming close to the quality of what those masters wrote. Mozart and Beethoven were so prolific that there's always tons of music to discover and every new generation discovers it for themselves anyway.