Storage multiplies and becomes more expensive once you're replicating across regions, backing up into an eternally growing corpus, and so on.

But the biggest impediment by far were internet transport costs. I mean, they're still onerous for a lot of media-heavy sites, but it was much worse at the time. Offloading that to third parties made an incredible amount of sense.

It's actually kind of bizarre that there is an Imgur "community". I know the operation ran at a massive money-losing proposition for quite some time.