I don't know about anyone else but I have never been told "I'm sorry - we'd like to teach you about ATPL theory but since you're at university now its too easy so you'll have to keep guessing".
No, the ATPL subjects are not inherently difficult but try cramming them in amongst advanced thermodynamics, engineering materials, aerofluid dynamics, flight mechanics, and all the other "ics" and, as anyone who has done an engineering degree will tell you, its not easy! After the first year the number of students on my course was whittled down from 16 to 9 - the ones who left were all very intelligent, talented people, but they just couldn't manage the workload.
That is how the course is deliberately designed. Obtaining a degree in such a course proves to the likes of OAA, CTC etc that, aside from being able to absorb the material, you are capable of committing yourself to an intensive and challenging course for a significant period of time, having invested your own money and time in your ambitions. Isn't this exactly the sort of low-risk prospective student they are looking for?