It's usually just for your Record of Student Achievement, which is important if you intend on dropping out of school and going into an apprenticeship. Your employer refers to this document as proof of your academic results. However, if you finish high school these credentials are not considered in lieu of your Higher School Certificate. That said, your year 10 grade marks may decide what HSC courses you can access (e.g. Only the top 30 of the grade can do extension maths, etc.), so keep trying your best!