For many reasons, including:
1) There is not a single evidence of evolution.
2) Where did the unicellular organism from which other life forms evolved according to Darwin's theory came from?
3) Why hasn’t any form of development been observed?
We haven't seen a monkey turn into a human.
And why didn't man evolve into a stronger being?
4) The discovery of DNA (amino acids) completely eliminated this theory.
5- The theory of evolution is just a hypothetical theory that has no laboratory experiments, observations or scientific facts.