Most manufacturer skins are meant to provide new features to differentiate themselves from the competition, oftentimes things that can't be added through an app. (thenextweb.com)
It will largely look the same across various manufacturer skins, save for some stylistic choices. (howtogeek.com)
Also, not everyone likes the stock manufacturer skins / themes that they are «stuck» with on their smartphones. (gizcentral.com)