TLDR: Because they can. SSO is the one feature a SaaS company can use to force people that can afford it up to higher tiers when their usage remains low but th

TLDR: Because they can. SSO is the one feature a SaaS company can use to force people that can afford it up to higher tiers when their usage remains low but the the value to the customer is high enough to justify the tier increase because of a mandated SSO requirement etc.