So, my girl straightens her hair too. Personally, I don't understand why one would want to do that kind of persistent damage to your natural hair, but its part of how she images herself, so it's not something I have any opinion on. From the outside, the only conceivable reason to straighten is because that's what white normative dictates, but I'm sure there are practical reasons depending on the situation. Really, straightening your hair is something you should do only because it's integral to your identity, not because you're trying to conform.