User authentication establishes who somebody is before letting them into a system. In a screen or video platform it is inseparable from the question that actually matters operationally: who may publish what, and where.
A network with one shared login is a network with no accountability. When content appears that nobody meant to publish (and it will), there is no way to know who did it or to remove only their access. Individual accounts are the prerequisite for every other control.
The caveat is that authentication and authorisation get conflated, and the second is where signage platforms differ most. Knowing who someone is settles nothing about whether a regional manager can publish to a neighbouring region, or whether an agency can touch templates as well as assets. Ask to see the permission model, not the login screen.
Practical requirements for anything with more than a handful of users: SSO against the directory already in use, so leavers lose access when HR removes them rather than when somebody remembers; and enforced multi-factor authentication, because a signage platform is a publishing system pointed at the public.