Why is my tax filing asking for my parents ssn when i haven't been claimed by them on their taxes and support myself?

It sounds like you are subject to "kiddie tax." It's not just for kiddies. For 2019 you are subject to kiddie tax if you have unearned income, such as investment income, of more than $2,200, you are not filing a joint return, and any one of the following is true.
(1) You were under 18 at the end of 2019.
(2) You were 18 at the end of 2019 and your earned income (from working) is not more than half of your total support for the year.
(3) You were under 24 at the end of 2019, you were a full-time student, and your earned income (from working) is not more than half of your total support for the year.

The informal, but very common, name "kiddie tax" comes from the days when it only applied to children under 14. The age limit has been raised to where it can apply to adult children who are still in school, but the name has stuck.

The kiddie tax applies higher tax rates to your unearned income over $2,200. For 2019 you have a choice of using your parents' tax rate or the rates for trusts and estates. TurboTax asked whether you want to use "pre-TCJA rules." That means using your parents' rate, which is usually the best choice. Obviously, if you answer Yes, in order to calculate the tax at your parents' rate, TurboTax needs information from your parents' tax return.

However, there's a known bug in the TurboTax interview. Even if you answer No to using the pre-TCJA rules, it still asks for your parents' information. But it doesn't use the parents' information that you enter. It does the tax calculation correctly using the TCJA rules. So if you answered No, you can enter anything you like just to get through the questions.