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. You'll also usually find Netflix, Microsoft Office, Spotify, Linkedin, and who knows what else. Another round of crapware will also be included if you buy a phone from a carrier, i.e., all the Verizon apps and whatever space they want to sell to third parties. The average amount users are reporting is 60GB, but crapware deals change across carriers and countries, so it will be different for everyone.