Because it's a response on a level appropriate to the question. Someone who could ask that question seriously doesn't have a very good understanding of the ToE. If they can get to the point where they can see the flaws in the analogy, they should be able to see why the original question is stupid in the first place.
Next, Darwin did say that natural selection always preserves favorable variations and always destroys unfavorable variations. If that is so, we may not only wonder why there are still apes, we may also wonder how it came to be that there is more than one species on earth.
"Favorable" doesn't mean "best." Favorable vs. unfavorable really just means works vs. doesn't work. Grizzly bears and mice both work fine--they do really different things, but they each do them well. Humans and apes also both work fine.
But Darwin did say that natural selection always preserves favorable variations and exterminates the unfavorable ones. You see, the reality of nature is not the problem, it's what Darwin said about the reality of nature. That's the problem.
You don't need as many humans to type a script of Hamlet.
Unless they are union members.
Cheers!