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).