I dont understand if the people that came to the usa with the daca policy why did they never become?

No one "Came" to America with the DACA policy. It is not a form of immigration if that's what you are implying. If you were brought here as a child or baby by A family member or parents that were illegal, and you grew up in America, well America is your only home, its all you know. DACA protects these children who most are now adults serving our military, running businesses, college.. etc, It protects them from deportation. Yes they should now work on becoming United States Citizens and some of them have, others have not made it a #1 priority because they never dreamed of one day being deported since they are protected under this act..

Your question of "WHY DID THEY or WHY DIDN'T THEY ?" cant really be answered unless you go and ask someone who is personally protected under DACA... I'm sure you have problems in your life, why haven't you solved them by now?