Ask PG: Why did YC add a "Non-Profit" track (as opposed to "Social Enterprise")?

Congratulations on the new initiative to accept non-profit organizations/ideas into the Y Combinator program. I am sure this will inspire many social-minded entrepreneurs. However, with the recent/growing focus towards for-profit social entrepreneurship, hybrid social ventures and patient capital, I am curious why YC chose to highlight only one end of the "social enterprise spectrum"? Or, does this mean YC has always been open to for-profit social enterprises?