Single Sign On Feature - MUST BE FREE

Why SSO features require enterprise subscription with every other product? In most cases, I don't need the enterprise features EXCEPT the SSO, which is not the core business of the products I need. What are you doing about this? If this is an enterprise feature, I'd be happy to know why it is (beyond the obvious and annoying reason --> $$$). EDIT: here is an interesting link with the SSO wall of shame https://sso.tax/