I think your conflating ideal with what's acceptable. Ideally you should use peer reviewed journal articles. But for a lot of topics, particularly in some fields e.g accounting or finance, finding peer reviewed journal articles can be hard so using reputable newspapers such as the wall street journal (the exact newspaper quoted by Yale and USyd) is okay.
lol no one is saying use Sydney Morning Herald or the Baulkham Hills shire local paper or any newspaper, as proven certain reliable newspapers are acceptable.