As others have noted, plenty of these apps are using the ActionBar (which is a default widget starting with 3.0, with an unofficial, open-source compatibility library) and plenty are using Fragments (also standard starting with 3.0, with an official compatibility library).
Moreover, many of these apps (e.g. Boid, Pocket, Papermill) are explicitly Holo-themed, so, at a minimum, they're using the default widgets for design guidance even when they're not using them directly (for compatibility or other reasons).
As others have noted, plenty of these apps are using the ActionBar (which is a default widget starting with 3.0, with an unofficial, open-source compatibility library) and plenty are using Fragments (also standard starting with 3.0, with an official compatibility library).
Moreover, many of these apps (e.g. Boid, Pocket, Papermill) are explicitly Holo-themed, so, at a minimum, they're using the default widgets for design guidance even when they're not using them directly (for compatibility or other reasons).