Apart from that, SSO is just a handy feature that non-Enterprise customers usually don't need while Enterprise customers do, so it's ideal for differentiating customers. That said an Enterprise edition contains much more than SSO in many cases, e.g. audit logging, containerized deployments, extensive support, etc.. That's what you pay for with an Enterprise offering, the SSO feature is just a small part of that.
This isn’t true, IMO, most people just don’t realize there’s an alternative to one user account per service. We’ve convinced non-enterprise users to use an objectively bad solution of password managers because every SaaS service hides their SSO option behind enterprise pricing.
SaaS companies want to charge a lower price to price-sensitive customers like bootstrapping startups, and a higher price to price-insensitive customers like big corporations; and they need some way to draw the line. And the moment you've got time to waste on things like SOC2 that drive you towards SSO - you are a price-insensitive organisation.