Why are most Catholic monks not priests?

I was wondering why most monks aren't ordained. It seems like some monasteries are about half and half while others seem to have as few priests as necessary. This would make sense in medieval times when it wasn't possible for that many people to be highly educated but why today? Given that they are Catholic monks and probably just as educated as the priests why would they remain lay, especially in monasteries where many of the monks are priests? Is there a specific reason for this in some monasteries?