It is absolutely necessary to give an argument for the existence of these experiences.
I know that you believe you have them, and that I believe I have them, but that doesn't mean that they have any tangible reality, it just means that our brains store things in a way that they will respond "yes, I have conscious experience."
Alternatively, should I accept as real everything that a person believes they experience? A schizophrenic's voices are real? A memory of a past trauma that is, in fact, a false memory, proves that the past trauma is real? This is a very dangerous path to walk, accepting the validity of introspection as a means of investigating the world...