> I'm an IT consultant working for a private company

Makes sense for GP locally, I guess, but globally we’re all worse off when nobody is motivated to break free from the path of least resistance.

Security is part of the story (beats keep track of different usernames+passwords for every tool), but convenience is also a major factor.

Pretty much everything supports SAML. If you decide not to support one of the standard protocols for SSO, you'll lose out on customers. Your tool has to bring in a lot of benefit (and have no competition) to warrant upending a company's entire auth system for.