The question itself misleading in some ways. Every answer to a science question like "Why does X" is always answered by recourse to something in the universe. That is, all questions in science have an answer (even if we don't know it yet) that is always expressed in terms of something that's within the universe.
So "Why does the universe exist" cannot have a scientific answer or explanation because the things we need to use in an answer are the very things we are striving to explain the existence of.
So "Why does the universe exist" cannot have a scientific answer or explanation because the things we need to use in an answer are the very things we are striving to explain the existence of.


