If you’re transferring 5GB over 1KB packets over UDP or a satellite, the benefits are very clear. Without a fountain code, there are 5,000,000 packets you need to receive. Miss one packet, and your have to sit through another 4,999,999 packets and pray very hard that you get your packet reliably the next time.

With a fountain code, it’s not a problem. If you miss one packet, you have a 99% chance of making do with the 5,000,001st packet that comes. 99.9% of making do with the 5,000,002nd packet etc.

In other words, without a fountain code, if you want to reliably receive 1GB, and you miss a packet, your satellite will have to transmit 2GB just for your sake, which is expensive af. With a fountain code, it’ll only need to send 1.01GB.

It vastly reduces the chance of you receiving a packet that contains no new information. If you just rebroadcast the same packets over and over again, a receiver that has 999/1000 packets may have a very low chance of serendipitously receiving the packet they need.

Not an expert, but if you miss a packet with the looping you have to wait for that particular packet, whereas with the fountain it sounds like you can get that back quicker.