Why Astrological Predictions Go Wrong?

"I have studied it, you have not!", is the famous retort of Sir Isaac Newton when confronted by Edmond Halley, his student on the master's belief in astrology. There are those who protest that astrology is not a science since it does not conform to the principle of falliability. Every hypothesis is true till it is proved otherwise. Yet, there are people who swear by astrology. They would consult the stars endlessly on each and every issue and would let themselves be driven by their astrologer guides.
What will happen tomorrow? - is a query that can never be answered by  any science or art other than astrology. Science is about what has or can happen in the light of well-doctrined principles. A doctor can tell the state of a living being at a given time with all the tests performed and possibly expect improvement in health or otherwise. From times immemorial, it has been the seer who was relied upon. Nostradamus'  prophecies or Brahammam's predictions are known the world over. There is criticism that most often astrological predictions fail and hence, people lose faith in the claims of astrologers. The reasons are not  hard to seek!
Firstly, astrology has not evolved much from the age-old days. Still in India, people are trying to decipher old texts or translate them from Sanskrit. The mystery of 'Nadi Astrology' (predictions written on Palmyrah leaves) is not yet fully solved though some had made investigations. The owners of these leaves would not let out the secrets to anyone except their kith and kin for fear of losing their livelihood. Some dismiss these as rubbish while some hail them as the most complex of all mysteries. The principle appears to be that all planetary positions in a horoscope will repeat after an interval and so will the destinies of people.
Secondly, there is no formal education in occult subjects, though, a few universities have, of late, initiated some diploma courses. Most of the astrologers learn by self-study while approach a Guru. Proficiency levels vary and are also questionable. Some have 'discovered' some opinions based on statistics while some have claimed that their understanding is superior to others. There are different aspects in Indian Astrology like 'Hora Shastra','Stree Jataka','Nashta Jataka', 'Muhurtha','Prasna' etc. There are also different methods and systems like 'Parasari','Jaimini','Kala Chakra' etc. Complete mastery even in one school of thought differentiates the best from the beast!
Thirdly, there are many assumptions and presumptions which are ignored. Basically, three data are essential :- Time of Birth, Date of Birth and Place of Birth. After casting the horoscope either by computer or manually, the astrologer gets ready to judge and predict based on a set of principles. But there are issues! First, what is meant by time of birth? Is it the first cry of the baby, or is it the touching of  ground, or is it the time when the umbilical cord is cut? It has also been opined that the time of conception is more important. Second, there is a dispute about the 'ayanamsa' or precession. Most of the astrologers adopt the value given by Lahiri. The late Dr.B.V.Raman had advocated the 'Raivatha Paksha Ayanamsa'. Krishnamurthy had given another. The Western counter-part is lucky in that he follows the 'Sayana' method  wherein the first point of Aries is considered movable. In other words, a horoscope casted by the Western Tropical method (Sayana), say, locates Jupiter in Aries,in the other chart casted by the Eastern Sidereal method (Nirayana) may place it in Pisces!
Lastly, opinions differ about signs and houses. The 'bhava' (house) chart can be different depending upon the system adopted for calculations. Many Indian astrologers adopt the Equal House system but are mostly unaware when to use the 'Rasi' chart and when the 'Bhava' chart. A salient point, however, remains. What is a rising sign? Is it right to consider it as the cusp?