Why does a Muslim begin by first learning the essential Sharia sciences?

Islam has urged the pursuit of knowledge, and among the proofs for this are Allah's saying: "Recite in the name of your Lord who created," and His saying: "Say, 'Are those who know equal to those who do not know?'" And the Prophet, peace be upon him, said: "Seeking knowledge is an obligation upon every Muslim." If a Muslim has not reached puberty, there is no harm in him learning non-essential sciences. As for the adult who does not know matters of creed and rulings of worship, he must begin with the essential knowledge upon which the correctness of his belief and worship depends.