Too many times, guidance is the synonym of a burden a few unlucky ones must bear.
A selfish view, of course, because we're very quick to forget we too also once needed guidance for something else.
Therefore, it's unfair for the senior consultant to guide the new intern because his time has become too important. And because it's ridiculous that he has to teach what is already so entrenched in his head that he actually forgot how to explain it.
This rots the passing of knowledge and know-how, usually stopping organizations from fulfilling their team's true potential. Not to mention the motivational issues for new kids who just want a chance to grow and make a difference.
Nothing is really obvious, specially for newcomers. It's a shame success tends to make you forget that.