If you don't hear at least a sentence a day where you haven't the slightest clue what was said, then I suspect you don't encounter many humans.

You're exaggerating, but thats ok. If I don't, then I simply ask them to clarify.

This could be a personal shortcoming but I am frequently left clueless what was meant. For low volume interactive situations asking for clarification is fine as long as the domain is simple.

Gathering requirements is generally done in natural language, but it's a very slow error-prone process. Even after sign-off on requirements it's pretty standard for them to be wrong in critical ways. Frankly this is the part of many software development projects that dooms them to failure.

Ignoring the difficulty of actually getting precise natural language, you'll still get to the point where no one can understand the language. If you don't believe me, go read some Kant.

I'd appoligize for the rambling comment with grammatical and spelling mistakes, but they further my point :)

This is key. We don't generally build computer systems that are capable of asking for clarification, but we should.

An error rate of 1/1,000 or so, with almost all of them being recoverable errors? I'll take that. :)