Oh honey, I can feel the sadness and desperation in your post. I wish I could make you a cup of tea and tell you it's going to be alright.
But you are correct only your parents can decide to get help. Also know you are in no way responsible for their choices. You probably know that intellectually, but I hope you really know deep down that their drinking isn't because they don't love you or there is something wrong with you. They have an addiction and with that comes deep denial.
You deserve parents who are sober and present for you. You really do deserve that and it breaks my heart they aren't able to show up for you.
But you are not alone. Unfortunately, there are LOTS of people your age who struggle with alcoholic parents. There is a program called Alateen specifically for teens dealing with this issue.
Do you have any family members you can trust who can help you get to a meeting? You will find others your age who understand exactly what you are going through.