Holo provides a consistent look and feel for core components.
When designing an Android app, you are free to provide your own
theme, but using Holo will guarantee a consistent look across
devices, and reduce the need to extensively test your brand-
speciﬁc theme with the many other themed variants of Android.
Thanks to Holo, the Twitter image picker interface
The Holo-themed settings
screen on a Galaxy Nexus
The customized settings
screen on a Xiaomi M2S