We can take a few guesses as to why things are so big. First, Samsung is notorious for having a shoddy software division that pumps out low-quality code. The company tends to change everything in Android just for change's sake, and it's hard to imagine those changes are very good.

...

Unlike the clean OSes you'd get from Google or Apple, Samsung sells space in its devices to the highest bidder via pre-installed crapware. A company like Facebook will buy a spot on Samsung's system partition, where it can get more intrusive system permissions that aren't granted to app store apps, letting it more effectively spy on users.

Urgh, it's so frustrating that Samsung is the leading Android manufacturer, the market is rewarding greed and incompetence