The problem with single user accounts in large organizations is multiple-fold:
With a single-user account, the forms, along with the data collected, technically belongs to the user. If and when this person leaves your organization, the forms and data leave, too. That data should belong to the organization, but with a single-user account, it doesn’t. With Jotform Enterprise, the Administrator can simply assign the seat to another user, ensuring the data stays within your organization.
Additionally, a single-user account is disconnected from other Jotform accounts. This means there is no opportunity to share and collaborate on forms already created, or access to data on other users' accounts.
Every single access to submission data needs to be traceable to a unique individual with his or her own identifiable login credentials, for IT audit purposes. With single user plans, because there is no way to share data, users may elect to share the login credentials, which is a violation of Jotform’s terms of use.
Note that this last item becomes an even larger legal issue as HIPAA regulations dictate that every single access to PHI (Protected Health Information) needs to be traceable to a unique individual with their own identifiable login credentials.