Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v1.c5.19

v1.c5.19

It is true that the number of works on astronomy is enormous. As however ours is a very extensive country, a multiple of works devoted to the same subject of every day use were compiled in different provinces. Again, some works, specially the Karaṇa works, became obsolete and useless in course of time, which also gave rise to different works in different ages; further, several people appear to have compiled several works on the same subject because it depends more or less on the ingenuity of the author or whether his work would be found to be perspicuous or not. These are some of the reasons for the multiplicity of astronomical works and their wide-spread currency.