It should be noted before answering the above-mentioned question that however, all of the divine laws are based upon securing the interests of mankind and keeping them away from harms. This means that nothing is lawful and unlawful without reason and it is not the case that things have been applied without any rhyme or reason, but the human is not able to comprehend all the benefits and harms on their own intellectual reason, only. Because, the one must follow Allah's revelation and infallibles' speeches. As a result, we must find out the real reason related to the above-mentioned question, from the Holy Quran and Sunna.
It should be said that however some obligatory acts can be performed optionally; which means we are able to do another act instead of the first we wanted to do. E.g. one has the option to make up his missed fast (that he missed it deliberately) by doing these kinds of atonements: 1. to fast sixty days, 2. to feed sixty poor 3. Or to give each of them one Sir of food (Sir is the old weight that almost equal to75 grammes).[1] But, according to many traditions (Ahadith), other acts cannot be substituted for the prayer. This means that we must perfume the prayer itself. Moreover, the prayer is the condition of accepting other good acts. Like this tradition in which says: "If your prayer is accepted by Allah the Almighty, your other acts of worship will be accepted too. If not they won't be accepted too."[2]
Therefore, when we have no real reason for substituting, we couldn’t act upon our opinions. E.g. if a patient has a variety of diseases and the Dr. prescribed some especial drugs for each of his illnesses, the patient is not able to use another drug (like heart drug) instead of  what the Dr. prescribed it (diabetes drug). So, we cannot leave the prayer and making it up by doing some Mustahab (recommended) or other Wajib acts of worship instead.
However, there is a possibility for those whose night prayer became gaza (missed it) to make it up by giving Sadagha (alms) to others.[3]

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