A common need for this is during an acquisition or merger. It's fine and all to assume that domain is identity, but that doesn't actually map too well to relat

A common need for this is during an acquisition or merger. It's fine and all to assume that domain is identity, but that doesn't actually map too well to relatively complex organizational hierarchies. Ex - Bank A and Bank B merge. There is going to be a period where they have to navigate that two domains represent a single organization. It's often a fairly high level of effort to move to a completely new domain, and it won't be done overnight. Yes - eventually you want to be back on a single domain, and I think there is definitely a world where this leads to some very bad patterns (HR and healthcare are two examples - if you've ever seen a login need to bounce between like 5 different domains because they've refused to actually do the technical work to consolidate back on a single domain, and treat the domain as marketing). But it's a really valid spot to end up in, and is the most common cause of having a single entity spread out over multiple domains in my experience.