Unfortunately, a need for SSO is about the only reliable way to gouge a large corporation. As a small fish you may like SSO, want SSO, you may even think you need SSO, but you really can get by without just fine. You're small - you can get around the requirements, or pivot, or whatever. A corporation is big and slow and can easily get themselves into a situation where not adding SSO will become a blocker for deals denominated in double-triple digit millions, but abandoning your product or the whole business segment will cost similar amount of money. In that situation, the vendor can have a field day milking the cash cow.