Some needs are so deeply wired into us – like the need to be loved, especially by our parents – that no matter how hard we rationalise and fight our emotions, we will always want to fill that gap one way or another. It is especially heartbreaking in the case of abuse or otherwise failed parenting, because the one person who had to love and protect you unconditionally, didn't. Overcoming the "why" in that question is probably a lifelong struggle with(in) oneself.