You do not have to build anything to use apps, and you do not pay extra for them. The Screenly App Store is a catalogue of ready-made ones, covering what screens most often need to show: dashboards, calendars, news, weather, a clock, a countdown. They come with your subscription, so you pick one, give it a few details, and drop it into a playlist.
For most needs, a ready-made app is enough. But your organization may have something specific to put on screen, a metric from your own systems, a board laid out exactly the way you want, and no catalogue can cover every case.
When it is missing, you are not stuck with what is there. You can request an app, and what customers ask for shapes what we add to the store next.