I want large companies to pay you too, but SSO is not a purely large company feature. There are plenty of companies with more than 10 developers that are not large companies.
This should cover all companies with 10 developers.
Edit: People here do get what you're saying - "This is the only way we can force some users to pay". What you're not hearing is "Either don't call out your software as FOSS, or if you do, figure out ways of price discriminating without hurting security for FOSS users."