Because you experience it? If you do..
The difference between the idea of qualia and the other properties that we granted special status to and then later refuted, is that in the latter cases we were trying to explain something external that we thought we were observing, whereas with subjective experience we are discussing a phenomenon that we (or at least some of us) directly, infallibly observe. It is not possible for me to be mistaken about whether there is something it is like to be me; it is not possible for me to be mistaken about whether what I experience is what I experience. It is possible for me to be mistaken about whether there is something it is like to be you, because I cannot directly observe your internal experience.