Its to reduce their maximum bandwidth capacity required. I don't see it as a problem, considering their price points. They're selling you storage, not "slam 1TB of your data into our storage system in a day". If you're looking for that, ship a hard drive to Iron Mountain.
EDIT: Even AWS limits how fast you can upload to S3, and built an appliance for you to rent and ship back and forth if you need to move data faster. That station wagon full of tape is still alive and well.