When you suddenly realize that your "big" data is not really that big!. Who needs a Hadoop/Spark cluster when you can run one of these bad boys
IIRC, the images for the site were closer to 7-8TB, but I don't know how typical that is for other types of sites, and caching every image on the site in memory is pretty impractical... just the same... damn.
The reason is so if you fuck up a scaling script for example you can't launch 1000 machines and take all the capacity and then bitch that you won't pay for it.
It's a stop gap.
However, aside from the hard limit of 100 S3 buckets, all other limits are configurable at the request of your AWS rep
https://aws.amazon.com/about-aws/whats-new/2015/08/amazon-s3...