The other companies have significantly different SLAs and drop packets far more readily. They also charge for bandwidth, in my experience, you get your 1TB/mo with your $5 VPS sure, but once you go over, you're facing per/GB charges that are very close to AWS default egress price.
They're not a magnet for these services for the reasons I just described as you reach your per VPS limit very quickly, and to get more "cheap bandwidth" you have to be prepared to run 100s of VMs per provider, and have to consider provisioning VMs you don't need just to get access to another $5 TB of transfer, or you're just going to end up paying the per GB fee anyways.
The terms aren't worse, but the service and their guarantees are different. Again, if you ask AWS for a bandwidth deal, they'll cut you one within a few minutes that will more than halve the price of your transfer if you pay up front. Which is AWSs way of saying, "if you make your usage predictable, we can make it way cheaper."
Why? Because they have fixed _capacity_ on their links. The costs manage that _capacity_.