Part of the problem is that pseudo code would likely be very hard to parse for a computer and many of the constructs are not efficient. Pseudo code often doesn't deal with how something is specifically done.

Secondly it usually relies extensively on a textual explanation. You can seldom use the pseudo code alone. It needs to be acomponied by an explanation in natural language.

Also pseudo code may simply skip trivial parts, as a human can fill in the blanks. A computer cannot easily do that. For pseudo code to really work, I think you would need an AI to parse it.