This is one way of trying to support those who decide to eventually leave the religion, as is their choice. Imagine you had been born into a conservative Muslim family. You did not have any financial independence and were sent to school without money. Your family fasted and expected you to as well. Secretly you didn't believe in God at all and thought the whole religion was a load of nonsense, but you knew that even if you did drink water during the day before your exam it would quite possibly be noticed by someone else in the community and get back to your furious parents. As a result you have little choice but to fast, and because no timetable changes have been made you sit both your maths and english exams on very hot June afternoons having not had a drink or anything to eat since 4AM the previous night and having already sat other papers in the morning. You achieve D grades in both.
After leaving home you decide to stop practicing Islam and fasting. However, the fact you have to re-sit these papers delays your education and employment, you are less likely to ever achieve top grades even in re-takes and employers can see you initially failed. As a result of this, you miss out on your dream job. You are effectively being punished for the faith of your parents - that isn't right, especially when it wasn't even your decision in the first place.