When I was 17 my mom helped me get a job at a cafeteria. She knew someone who new of a job in a cafeteria and that is often the way things can happen. Your parents have totally different connections than you do and they might be able to get some job leads though people they know or work with.
Jobs for 17 year olds just aren't going to come knocking on your door at this stage. To get a job now you probably need help from someone who has an "in" with an employer or someone who happens to know of an open job. By getting your parents to ask around on your behalf, you will have more of a chance of making a connection with someone that can lead you to a job opening.
Many teenagers are hesitant to ask their parents for help, no matter what the situation is. They are too concerned about getting respect and looking like they don't need anyone's help. Sadly, many teenagers don't even have a good relationship with their parents for a variety of reasons.
But this is the time to put all differences aside and ask them for assistance. The economy is not going to get any better this summer and 17 year olds needing a job need to find one right away. Asking your parents to help in the job hunt is a smart thing to do even if it might not be what you want to do.