Rasterization affects how basic text and 3D text interact with other objects in your project.
If a text layer in a nonrasterized 2D group is set to a blend mode, such as Soft Light, it interacts with images in groups beneath it in the layer stack. After the 2D group is rasterized, the Soft Light blend mode no longer interacts with the layer beneath it.
Tip: In this case, moving the image into the group that contains the text eliminates the rasterization issue.
Sometimes, text is rasterized independently of the group in which it resides, and that rasterization affects how the text interacts with objects in its own group. For example, applying a Circle Blur filter to text that exists in 3D space (such as text on a path) causes the text to no longer intersect with other objects in the same group. The same operations that cause a 3D group to rasterize cause 3D text to rasterize. In some situations, selecting the Flatten checkbox in the Layout pane of the Text Inspector can minimize this effect.
For more information on rasterization in 2D and 3D groups, see Groups and rasterization.