Why is it that an ARBITRARY distinction is being made between what you have defined as evolution and explanations for the origin of life?
It's two different fields. It's no more arbitrary, or no less, than the distinction between the study of biology and the study of chemistry.
Evolution is a theory in biology, it explains the history and diversity of life on Earth in terms of changing gene frequencies by mutation and natural selection. Since the genes themselves are
chemical things,
their origin must obviously be a study for the field of
chemistry.
Ultimately it's all the study of the same universe. Just because we don't know for sure how life
began doesn't mean we can't come to conclusions about what's been happening
since.