Earlier quoted context omitted.
Unfortunately, some services don’t allow this.
Ideally they would support SSO, but at a minimum any service that wants business customers will have accounts in some form. If they don't even have that then I would seriously second guess using them for anything in production. They're clearly not designed for businesses and can't be relied upon to not screw you up in serious ways.
I mean, that's just not true. Plenty of successful and widely used businesses out there provide a single account/password for their service at a client company, rather than for each human user at that client company. It's a common pattern even if you think it shouldn't be. And yes they are designed for businsses and have business customers.
For a lot of products, it's just not conceptually necessary to have multiple users for an account, i.e. support for "teams". It's a convenience that might be on the roadmap and might get done eventually, or not at all. Especially because supporting complex sets of user credentials can be a major project, which means another important feature doesn't get done instead.