Spatial Anchors - why track them per frame?

I'm learning about spatial anchors. My test app can create them, make them persistent between sessions and query them at startup.

So at the start of the app, you can query them, make them trackable and display specific content at their location. My question is ... why does the sample app track them and update the contents pose attached each frame? I would think that the anchor would remain in the same location and pose until the app moves it based on physics or player interaction.

What am I missing?