Why did i have to fill out a SF86 and have a interview? 10 points worth?

im in army dep and i signed up for 74d, i do not qualify for security celarance because i have a criminal background(2 misdeamnors and traffic tickets) and plus mos 74d doesnt require any kind of clearance...i filled out the long form and also had to meet with a investigator and GRILLED me on my criminal history and where i lived, etc for 3 hours straight! my moral waivers was approved already....why did i have fill that form out and plus have a interview??? i dont ship out until may 2011....is there a possibility i will be discharged from dep???? plz help,