So why didn't she? This was one of the mistakes they made imo.
A lawyer will always err on the side of caution, the McCann's lawyer didn't know if they were guilty or innocent any more than the police did. If Kate was completely innocent she should have answered every question put to her and more.
In addition, continually criticising the police who were trying to find your missing child was a no-brainer for stupidity.
She didn't because she was advised not to, it's as simple as that. In the same position, you might well be advised to do the same even if you're innocent. Did you not watch the video clip I posted a couple of weeks back about why you should NEVER answer police questions, even if you've nothing to hide? It was very thought-provoking IMO.
And in addition, criticising the police for concentrating all their efforts on proving you've dunnit (when you haven't) instead of looking for the person who did is perfectly justifiable - IMO again.