This isn't a "billion-dollar business"; it's an overhyped company that gives credit cards to startups that raised money at a billion-dollar valuation. They may

This isn't a "billion-dollar business"; it's an overhyped company that gives credit cards to startups that raised money at a billion-dollar valuation. They may have already reached their entire market for their existing business; the billion-dollar valuation only makes sense if they can plan to grow into other credit card markets.