Speaking as a DS (with a PhD), we tend to look for people with PhDs not because of specific domain knowledge, but because those people have learned how to conduct large scale, long term research independently. Despite what people tell you, this is a skill that must be learned and is one of the rites of passage of grad school. Can you assess a large, open ended problem? Get the data? Do a literature search? Rapidly acquire the theory and math necessary? Apply it? Kaggle competitions and courses are nice, but a short term project with a pre-selected data set doesn't represent the reality at our company for a DS. Without a PhD, I'd need to see a portfolio with significant long term (6 months or more) real research projects to be considered.