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.