Because 50 gigs is next to nothing, and you only need a rinky dink amount of compute to write files.

YouTube, on the other hand, is actually pretty expensive to operate. Takes a lot of storage to store videos, never mind handling uploads. But then streaming video? Man, the amount of bandwidth required for that makes file syncing look like nothing. I mean, how often does a single customer watch a YouTube video? And then, how often do people download files from Dropbox? It's orders of magnitude in difference.

But LLMs outshine both. They require stupid amounts of compute to run.